Commit Graph

85 Commits

Author SHA1 Message Date
Laura Abbott c6517b7815 doc: ioctl: Add some clarifications to botching-up-ioctls
- The guide currently says to pad the structure to a multiple of
  64-bits. This is not necessary in cases where the structure contains
  no 64-bit types. Clarify this concept to avoid unnecessary padding.
- When using __u64 to hold user pointers, blindly trying to do a cast to
  a void __user * may generate a warning on 32-bit systems about a cast
  from an integer to a pointer of different size. There is a macro to
  deal with this which hides an ugly double cast. Add a reference to
  this macro.

Signed-off-by: Laura Abbott <labbott@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2016-09-06 06:00:22 -06:00
Ryusuke Konishi e63e88bc53 nilfs2: move ioctl interface and disk layout to uapi separately
The header file "include/linux/nilfs2_fs.h" is composed of parts for
ioctl and disk format, and both are intended to be shared with user
space programs.

This moves them to the uapi directory "include/uapi/linux" splitting the
file to "nilfs2_api.h" and "nilfs2_ondisk.h".  The following minor
changes are accompanied by this migration:

 - nilfs_direct_node struct in nilfs2/direct.h is converged to
   nilfs2_ondisk.h because it's an on-disk structure.
 - inline functions nilfs_rec_len_from_disk() and
   nilfs_rec_len_to_disk() are moved to nilfs2/dir.c.

Link: http://lkml.kernel.org/r/1465825507-3407-4-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02 19:35:21 -04:00
Linus Torvalds 7a1e8b80fb Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates from James Morris:
 "Highlights:

   - TPM core and driver updates/fixes
   - IPv6 security labeling (CALIPSO)
   - Lots of Apparmor fixes
   - Seccomp: remove 2-phase API, close hole where ptrace can change
     syscall #"

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (156 commits)
  apparmor: fix SECURITY_APPARMOR_HASH_DEFAULT parameter handling
  tpm: Add TPM 2.0 support to the Nuvoton i2c driver (NPCT6xx family)
  tpm: Factor out common startup code
  tpm: use devm_add_action_or_reset
  tpm2_i2c_nuvoton: add irq validity check
  tpm: read burstcount from TPM_STS in one 32-bit transaction
  tpm: fix byte-order for the value read by tpm2_get_tpm_pt
  tpm_tis_core: convert max timeouts from msec to jiffies
  apparmor: fix arg_size computation for when setprocattr is null terminated
  apparmor: fix oops, validate buffer size in apparmor_setprocattr()
  apparmor: do not expose kernel stack
  apparmor: fix module parameters can be changed after policy is locked
  apparmor: fix oops in profile_unpack() when policy_db is not present
  apparmor: don't check for vmalloc_addr if kvzalloc() failed
  apparmor: add missing id bounds check on dfa verification
  apparmor: allow SYS_CAP_RESOURCE to be sufficient to prlimit another task
  apparmor: use list_next_entry instead of list_entry_next
  apparmor: fix refcount race when finding a child profile
  apparmor: fix ref count leak when profile sha1 hash is read
  apparmor: check that xindex is in trans_table bounds
  ...
2016-07-29 17:38:46 -07:00
vchannaiah bf294e833b cdrom: support read sub-channel command in LBA format
userspace application can send READ_SUB_CHANNEL command with time bit
enabled and disabled. The time bit allows selection of address reporting
format. If the time bit is disabled the response is in logical block
address(CDROM_LBA) format, represented as a 32-bit integer with ms-byte
first. If the time bit is enabled the response is in time format i.e.,
minutes, second, frame (CDROM_MSF) format.

Signed-off-by: vchannaiah <vanitha.channaiah@in.bosch.com>
Signed-off-by: Mahendran Kuppusamy <mahendran.kuppusamy@in.bosch.com>
[veeraiyan.chidambaram@in.bosch.com: updated Documentation/ioctl/cdrom.txt]
Signed-off-by: Veeraiyan Chidambaram <veeraiyan.chidambaram@in.bosch.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-07-12 08:24:50 -07:00
Stefan Berger 7e1dc002c0 tpm: Add documentation for the tpm_vtpm_proxy device driver
Add documentation for the tpm_vtpm device driver that implements
support for providing TPM functionality to Linux containers.

Parts of this documentation were recycled from the Xen vTPM
device driver documentation.

Update the documentation for the ioctl numbers.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

CC: linux-kernel@vger.kernel.org
CC: linux-doc@vger.kernel.org
CC: linux-api@vger.kernel.org
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
2016-06-25 17:26:35 +03:00
Linus Walleij fae9816446 gpio: uapi: use 0xB4 as ioctl() major
The previous 'o' is in conflict and not very orderly assigned.
We want to select an ioctl() major that does not conflict with
the existining ones.

Add the new reserved major (0xB4) to Documentation/ioctl/ioctl-number.txt

Fixes: 3c702e9987 ("gpio: add a userspace chardev ABI for GPIOs")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2016-03-10 16:02:52 +07:00
Masanari Iida d53a7b8ff6 Doc: ioctl: Fix typos in Documentation/ioctl
This patch fix some spelling typos in Documentation/ioctl.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2015-11-20 16:52:50 -07:00
Linus Torvalds 8e483ed134 Merge tag 'char-misc-4.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull char/misc driver updates from Greg KH:
 "Here is the big char/misc driver update for 4.4-rc1.  Lots of
  different driver and subsystem updates, hwtracing being the largest
  with the addition of some new platforms that are now supported.  Full
  details in the shortlog.

  All of these have been in linux-next for a long time with no reported
  issues"

* tag 'char-misc-4.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (181 commits)
  fpga: socfpga: Fix check of return value of devm_request_irq
  lkdtm: fix ACCESS_USERSPACE test
  mcb: Destroy IDA on module unload
  mcb: Do not return zero on error path in mcb_pci_probe()
  mei: bus: set the device name before running fixup
  mei: bus: use correct lock ordering
  mei: Fix debugfs filename in error output
  char: ipmi: ipmi_ssif: Replace timeval with timespec64
  fpga: zynq-fpga: Fix issue with drvdata being overwritten.
  fpga manager: remove unnecessary null pointer checks
  fpga manager: ensure lifetime with of_fpga_mgr_get
  fpga: zynq-fpga: Change fw format to handle bin instead of bit.
  fpga: zynq-fpga: Fix unbalanced clock handling
  misc: sram: partition base address belongs to __iomem space
  coresight: etm3x: adding documentation for sysFS's cpu interface
  vme: 8-bit status/id takes 256 values, not 255
  fpga manager: Adding FPGA Manager support for Xilinx Zynq 7000
  ARM: zynq: dt: Updated devicetree for Zynq 7000 platform.
  ARM: dt: fpga: Added binding docs for Xilinx Zynq FPGA manager.
  ver_linux: proc/modules, limit text processing to 'sed'
  ...
2015-11-04 22:15:15 -08:00
Matias Bjørling cd9e9808d1 lightnvm: Support for Open-Channel SSDs
Open-channel SSDs are devices that share responsibilities with the host
in order to implement and maintain features that typical SSDs keep
strictly in firmware. These include (i) the Flash Translation Layer
(FTL), (ii) bad block management, and (iii) hardware units such as the
flash controller, the interface controller, and large amounts of flash
chips. In this way, Open-channels SSDs exposes direct access to their
physical flash storage, while keeping a subset of the internal features
of SSDs.

LightNVM is a specification that gives support to Open-channel SSDs
LightNVM allows the host to manage data placement, garbage collection,
and parallelism. Device specific responsibilities such as bad block
management, FTL extensions to support atomic IOs, or metadata
persistence are still handled by the device.

The implementation of LightNVM consists of two parts: core and
(multiple) targets. The core implements functionality shared across
targets. This is initialization, teardown and statistics. The targets
implement the interface that exposes physical flash to user-space
applications. Examples of such targets include key-value store,
object-store, as well as traditional block devices, which can be
application-specific.

Contributions in this patch from:

  Javier Gonzalez <jg@lightnvm.io>
  Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
  Jesper Madsen <jmad@itu.dk>

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-10-29 16:21:42 +09:00
Alexander Shishkin 7bd1d4093c stm class: Introduce an abstraction for System Trace Module devices
A System Trace Module (STM) is a device exporting data in System Trace
Protocol (STP) format as defined by MIPI STP standards. Examples of such
devices are Intel(R) Trace Hub and Coresight STM.

This abstraction provides a unified interface for software trace sources
to send their data over an STM device to a debug host. In order to do
that, such a trace source needs to be assigned a pair of master/channel
identifiers that all the data from this source will be tagged with. The
STP decoder on the debug host side will use these master/channel tags to
distinguish different trace streams from one another inside one STP
stream.

This abstraction provides a configfs-based policy management mechanism
for dynamic allocation of these master/channel pairs based on trace
source-supplied string identifier. It has the flexibility of being
defined at runtime and at the same time (provided that the policy
definition is aligned with the decoding end) consistency.

For userspace trace sources, this abstraction provides write()-based and
mmap()-based (if the underlying stm device allows this) output mechanism.

For kernel-side trace sources, we provide "stm_source" device class that
can be connected to an stm device at run time.

Cc: linux-api@vger.kernel.org
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04 20:28:58 +01:00
Linus Torvalds 3af6e98f25 Merge tag 'platform-drivers-x86-v4.3-1' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86
Pull x86 platform driver updates from Darren Hart:
 "Significant work on toshiba_acpi, including new hardware support,
  refactoring, and cleanups.  Extend device support for asus, ideapad,
  and acer systems.  New surface pro 3 buttons driver.  Misc minor
  cleanups for thinkpad and hp-wireless.

  acer-wmi:
   - No rfkill on HP Omen 15 wifi

  thinkpad_acpi:
   - Remove side effects from vdbg_printk -> no_printk macro

  surface pro 3:
   - Add support driver for Surface Pro 3 buttons

  hp-wireless:
   - remove unneeded goto/label in hpwl_init

  ideapad-laptop:
   - add alternative representation for Yoga 2 to DMI table
   - Add Lenovo Yoga 3 14 to no_hw_rfkill dmi list

  asus-laptop:
   - Add key found on Asus F3M

  MAINTAINERS:
   - Remove Toshiba Linux mailing list address

  toshiba_acpi:
   - Bump driver version to 0.23
   - Remove unnecessary checks and returns in HCI/SCI functions
   - Refactor *{get, set} functions return value
   - Remove "*not supported" feature prints
   - Change *available functions return type
   - Add set_fan_status function
   - Change some variables to avoid warnings from ninja-check
   - Reorder toshiba_acpi_alt_keymap entries
   - Remove unused wireless defines
   - Transflective backlight updates
   - Avoid registering input device on WMI event laptops
   - Add /dev/toshiba_acpi device
   - Adapt /proc/acpi/toshiba/keys to TOS1900 devices"

* tag 'platform-drivers-x86-v4.3-1' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86: (21 commits)
  acer-wmi: No rfkill on HP Omen 15 wifi
  thinkpad_acpi: Remove side effects from vdbg_printk -> no_printk macro
  surface pro 3: Add support driver for Surface Pro 3 buttons
  hp-wireless: remove unneeded goto/label in hpwl_init
  ideapad-laptop: add alternative representation for Yoga 2 to DMI table
  asus-laptop: Add key found on Asus F3M
  MAINTAINERS: Remove Toshiba Linux mailing list address
  ideapad-laptop: Add Lenovo Yoga 3 14 to no_hw_rfkill dmi list
  toshiba_acpi: Bump driver version to 0.23
  toshiba_acpi: Remove unnecessary checks and returns in HCI/SCI functions
  toshiba_acpi: Refactor *{get, set} functions return value
  toshiba_acpi: Remove "*not supported" feature prints
  toshiba_acpi: Change *available functions return type
  toshiba_acpi: Add set_fan_status function
  toshiba_acpi: Change some variables to avoid warnings from ninja-check
  toshiba_acpi: Reorder toshiba_acpi_alt_keymap entries
  toshiba_acpi: Remove unused wireless defines
  toshiba_acpi: Transflective backlight updates
  toshiba_acpi: Avoid registering input device on WMI event laptops
  toshiba_acpi: Add /dev/toshiba_acpi device
  ...
2015-09-08 16:26:18 -07:00
Andrea Arcangeli 1038628d80 userfaultfd: uAPI
Defines the uAPI of the userfaultfd, notably the ioctl numbers and protocol.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 16:54:41 -07:00
Linus Torvalds df910390e2 Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
Pull first round of SCSI updates from James Bottomley:
 "This includes one new driver: cxlflash plus the usual grab bag of
  updates for the major drivers: qla2xxx, ipr, storvsc, pm80xx, hptiop,
  plus a few assorted fixes.

  There's another tranch coming, but I want to incubate it another few
  days in the checkers, plus it includes a mpt2sas separated lifetime
  fix, which Avago won't get done testing until Friday"

* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (85 commits)
  aic94xx: set an error code on failure
  storvsc: Set the error code correctly in failure conditions
  storvsc: Allow write_same when host is windows 10
  storvsc: use storage protocol version to determine storage capabilities
  storvsc: use correct defaults for values determined by protocol negotiation
  storvsc: Untangle the storage protocol negotiation from the vmbus protocol negotiation.
  storvsc: Use a single value to track protocol versions
  storvsc: Rather than look for sets of specific protocol versions, make decisions based on ranges.
  cxlflash: Remove unused variable from queuecommand
  cxlflash: shift wrapping bug in afu_link_reset()
  cxlflash: off by one bug in cxlflash_show_port_status()
  cxlflash: Virtual LUN support
  cxlflash: Superpipe support
  cxlflash: Base error recovery support
  qla2xxx: Update driver version to 8.07.00.26-k
  qla2xxx: Add pci device id 0x2261.
  qla2xxx: Fix missing device login retries.
  qla2xxx: do not clear slot in outstanding cmd array
  qla2xxx: Remove decrement of sp reference count in abort handler.
  qla2xxx: Add support to show MPI and PEP FW version for ISP27xx.
  ...
2015-09-02 12:22:54 -07:00
Matthew R. Ochs 65be2c79ac cxlflash: Superpipe support
Add superpipe supporting infrastructure to device driver for the IBM CXL
Flash adapter. This patch allows userspace applications to take advantage
of the accelerated I/O features that this adapter provides and bypass the
traditional filesystem stack.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
2015-08-26 18:04:37 -07:00
Tomas Winkler 3c7c8468e5 mei: add async event notification ioctls
Add ioctl IOCTL_MEI_NOTIFY_SET for enabling and disabling
async event notification.
Add ioctl IOCTL_MEI_NOTIFY_GET for receiving and acking
an event notification.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-08-03 17:30:00 -07:00
Azael Avalos fc5462f852 toshiba_acpi: Add /dev/toshiba_acpi device
There were previous attempts to "merge" the toshiba SMM module to the
toshiba_acpi one, they were trying to imitate what the old toshiba
module does, however, some models (TOS1900 devices) come with a
"crippled" implementation and do not provide all the "features" a
"genuine" Toshiba BIOS does.

This patch adds a new device called toshiba_acpi, which aim is to
enable userspace to access the SMM on Toshiba laptops via ACPI calls.

Creating a new convenience _IOWR command to access the SCI functions
by opening/closing the SCI internally to avoid buggy BIOS, while at
the same time providing backwards compatibility.

Older programs (and new) who wish to access the SMM on newer models
can do it by pointing their path to /dev/toshiba_acpi (instead of
/dev/toshiba) as the toshiba.h header was modified to reflect these
changes as well as adds all the toshiba_acpi paths and command,
however, it is strongly recommended to use the new IOCTL for any
SCI command to avoid any buggy BIOS.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
2015-07-24 14:15:10 -07:00
Miklos Szeredi 00c570f4ba fuse: device fd clone
Allow an open fuse device to be "cloned".  Userspace can create a clone by:

      newfd = open("/dev/fuse", O_RDWR)
      ioctl(newfd, FUSE_DEV_IOC_CLONE, &oldfd);

At this point newfd will refer to the same fuse connection as oldfd.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>
2015-07-01 16:26:08 +02:00
Bill Richardson e7c256fbfb platform/chrome: Add Chrome OS EC userspace device interface
This patch adds a device interface to access the
Chrome OS Embedded Controller from user-space.

Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-by: Simon Glass <sjg@google.com>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
2015-02-26 15:45:06 -08:00
Ian Munsie a9282d01cf cxl: Add documentation for userspace APIs
This documentation gives an overview of the hardware architecture, userspace
APIs via /dev/cxl/afuM.N and the syfs files. It also adds a MAINTAINERS file
entry for cxl.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2014-10-08 20:16:19 +11:00
Michael Ellerman efe4a77221 Documentation: add How to avoid botching up ioctls
I pointed some folks at this and they wondered why it wasn't in the
kernel Documentation directory. So now it is.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-09 09:13:40 -07:00
Tadeusz Struk cea4001ae1 crypto: qat - Update to makefiles
Update to makefiles etc.
Don't update the firmware/Makefile yet since there is no FW binary in
the crypto repo yet. This will be added later.

v3 - removed change to ./firmware/Makefile

Reviewed-by: Bruce W. Allan <bruce.w.allan@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-06-20 21:26:19 +08:00
Martin Schwidefsky 07be038209 s390/hypfs: add interface for diagnose 0x304
To provide access to the set-partition-resource-parameter interface
to user space add a new attribute to hypfs/debugfs:
 * s390_hypsfs/diag_304
The data for the query-partition-resource-parameters command can
be access by a read on the attribute. All other diagnose 0x304
requests need to be submitted via ioctl with CAP_SYS_ADMIN rights.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2014-01-24 09:40:59 +01:00
Clemens Ladisch 82fbb4f7b4 ALSA: add DICE driver
As a start point for further development, this is an incomplete driver
for DICE devices:
- only playback (so no clock source except the bus clock)
- only 44.1 kHz
- no MIDI
- recovery after bus reset is slow
- hwdep device is created, but not actually implemented

Contains compilation fixes by Stefan Richter.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
2013-10-17 21:18:32 +02:00
Michael Holzheu d475f942b1 s390/sclp: Add SCLP character device driver
Add a character misc device "sclp_ctl" that allows to run SCCBs
from user space using the SCLP_CTL_SCCB ioctl.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2013-06-26 21:10:13 +02:00
Bjørn Mork 3edce1cf81 USB: cdc-wdm: implement IOCTL_WDM_MAX_COMMAND
Userspace applications need to know the maximum supported message
size.

The cdc-wdm driver translates between a character device stream
and a message based protocol.  Each message is transported as a
usb control message with no further encapsulation or syncronization.
Each read or write on the character device should translate to
exactly one usb control message to ensure that message boundaries
are kept intact.  That means that the userspace application must
know the maximum message size supported by the device and driver,
making this size a vital part of the cdc-wdm character device API.

CDC WDM and CDC MBIM functions export the maximum supported
message size through CDC functional descriptors.  The cdc-wdm and
cdc_mbim drivers will parse these descriptors and use the value
chosen by the device.  The only current way for a userspace
application to retrive the value is by duplicating the descriptor
parsing. This is an unnecessary complex task, and application
writers are likely to postpone it, using a fixed value and adding
a "todo" item.

QMI functions have no way to tell the host what message size they
support.  The qmi_wwan driver use a fixed value based on protocol
recommendations and observed device behaviour.  Userspace
applications must know and hard code the same value.  This scheme
will break if we ever encounter a QMI device needing a device
specific message size quirk.  We are currently unable to support
such a device because using a non default size would break the
implicit userspace API.

The message size is currently a hidden attribute of the cdc-wdm
userspace API.  Retrieving it is unnecessarily complex, increasing
the possibility of drivers and applications using different limits.
The resulting errors are hard to debug, and can only be replicated
on identical hardware.

Exporting the maximum message size from the driver simplifies the
task for the userspace application, and creates a unified
information source independent of device and function class. It also
serves to document that the message size is part of the cdc-wdm
userspace API.

This proposed API extension has been presented for the authors of
userspace applications and libraries using the current API: libmbim,
libqmi, uqmi, oFono and ModemManager.  The replies were:

Aleksander Morgado:
 "We do really need max message size for MBIM; and as you say, it may be
  good to have the max message size info also for QMI, so the new ioctl
  seems a good addition. So +1 from my side, for what it's worth."

Dan Williams:
 "Yeah, +1 here.  I'd prefer the sysfs file, but the fact that that
  doesn't work for fd passing pretty much kills it."

No negative replies are so far received.

Cc: Aleksander Morgado <aleksander@lanedo.com>
Cc: Dan Williams <dcbw@redhat.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Acked-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-03-25 13:32:20 -07:00