linux.git/drivers/staging/comedi/range.c, branch v5.10.258

comedi: Fix getting range information for subdevices 16 to 255

2026-02-06T15:40:13+00:00

commit 10d28cffb3f6ec7ad67f0a4cd32c2afa92909452 upstream.

The `COMEDI_RANGEINFO` ioctl does not work properly for subdevice
indices above 15.  Currently, the only in-tree COMEDI drivers that
support more than 16 subdevices are the "8255" driver and the
"comedi_bond" driver.  Making the ioctl work for subdevice indices up to
255 is achievable.  It needs minor changes to the handling of the
`COMEDI_RANGEINFO` and `COMEDI_CHANINFO` ioctls that should be mostly
harmless to user-space, apart from making them less broken.  Details
follow...

The `COMEDI_RANGEINFO` ioctl command gets the list of supported ranges
(usually with units of volts or milliamps) for a COMEDI subdevice or
channel.  (Only some subdevices have per-channel range tables, indicated
by the `SDF_RANGETYPE` flag in the subdevice information.)  It uses a
`range_type` value and a user-space pointer, both supplied by
user-space, but the `range_type` value should match what was obtained
using the `COMEDI_CHANINFO` ioctl (if the subdevice has per-channel
range tables)  or `COMEDI_SUBDINFO` ioctl (if the subdevice uses a
single range table for all channels).  Bits 15 to 0 of the `range_type`
value contain the length of the range table, which is the only part that
user-space should care about (so it can use a suitably sized buffer to
fetch the range table).  Bits 23 to 16 store the channel index, which is
assumed to be no more than 255 if the subdevice has per-channel range
tables, and is set to 0 if the subdevice has a single range table.  For
`range_type` values produced by the `COMEDI_SUBDINFO` ioctl, bits 31 to
24 contain the subdevice index, which is assumed to be no more than 255.
But for `range_type` values produced by the `COMEDI_CHANINFO` ioctl,
bits 27 to 24 contain the subdevice index, which is assumed to be no
more than 15, and bits 31 to 28 contain the COMEDI device's minor device
number for some unknown reason lost in the mists of time.  The
`COMEDI_RANGEINFO` ioctl extract the length from bits 15 to 0 of the
user-supplied `range_type` value, extracts the channel index from bits
23 to 16 (only used if the subdevice has per-channel range tables),
extracts the subdevice index from bits 27 to 24, and ignores bits 31 to
28.  So for subdevice indices 16 to 255, the `COMEDI_SUBDINFO` or
`COMEDI_CHANINFO` ioctl will report a `range_type` value that doesn't
work with the `COMEDI_RANGEINFO` ioctl.  It will either get the range
table for the subdevice index modulo 16, or will fail with `-EINVAL`.

To fix this, always use bits 31 to 24 of the `range_type` value to hold
the subdevice index (assumed to be no more than 255).  This affects the
`COMEDI_CHANINFO` and `COMEDI_RANGEINFO` ioctls.  There should not be
anything in user-space that depends on the old, broken usage, although
it may now see different values in bits 31 to 28 of the `range_type`
values reported by the `COMEDI_CHANINFO` ioctl for subdevices that have
per-channel subdevices.  User-space should not be trying to decode bits
31 to 16 of the `range_type` values anyway.

Fixes: ed9eccbe8970 ("Staging: add comedi core")
Cc: stable@vger.kernel.org #5.17+
Signed-off-by: Ian Abbott 
Link: https://patch.msgid.link/20251203162438.176841-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman

comedi: get rid of compat_alloc_user_space() mess in COMEDI_RANGEINFO compat

2020-05-29T00:31:19+00:00

Just take copy_from_user() out of do_rangeing_ioctl() into the caller and
have compat_rangeinfo() build a native version and pass it to do_rangeinfo_ioctl()
directly.

Signed-off-by: Al Viro

staging: comedi: Remove redundant license text

2017-11-28T12:20:46+00:00

Now that the SPDX tag is in all comedi files, that identifies the
license in a specific and legally-defined manner.  So the extra GPL text
wording can be removed as it is no longer needed at all.

This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text.  And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.

No copyright headers or other non-license-description text was removed.

Cc: Ian Abbott 
Cc: H Hartley Sweeten 
Signed-off-by: Greg Kroah-Hartman

staging: comedi: add SPDX identifiers to all greybus driver files

2017-11-28T12:20:45+00:00

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the drivers/staging/comedi files files with the correct SPDX
license identifier based on the license text in the file itself.  The
SPDX identifier is a legally binding shorthand, which can be used
instead of the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Ian Abbott 
Cc: H Hartley Sweeten 
Cc: Thomas Gleixner 
Cc: Kate Stewart 
Cc: Philippe Ombredanne 
Signed-off-by: Greg Kroah-Hartman

staging: comedi: improve comedi_check_chanlist() documentation

2015-08-05T18:55:44+00:00

Signed-off-by: Ian Abbott 
Reviewed-by: H Hartley Sweeten 
Signed-off-by: Greg Kroah-Hartman

staging: comedi: range.c: reformat copyright comment

2015-02-07T09:04:22+00:00

Use the usual block comment style.

Signed-off-by: Ian Abbott 
Reviewed-by: H Hartley Sweeten 
Signed-off-by: Greg Kroah-Hartman

staging: comedi: range.c: reformat ioctl handler comment

2015-02-07T09:04:22+00:00

The unlocked_ioctl handler in "comedi_fops.c" calls a different function
to handle each supported ioctl command code.  Most of these have a block
comment indicating which command code it handles, a brief description,
and an informal description of the inputs and outputs.  These block
comments were formatted in various styles, but have been reformatted to
use the usual block comment style.

The block comment for the handler function for the `COMEDI_RANGEINFO`
ioctl code is in "range.c".  Reformat it to use the usual block command
style to match the others.  Reword it a bit for consistency.

Signed-off-by: Ian Abbott 
Reviewed-by: H Hartley Sweeten 
Signed-off-by: Greg Kroah-Hartman

staging: comedi: Remove unecessary function and it's call

2014-10-20T02:29:13+00:00

Function aref_invalid has unreachable code as it right now
just returns 0 after declaring a variable.
This patch removes this function and it's single call.

As it is static so it's obvious that it is not used anywhere
other than this file or somewhere, where this is included.
I also build tested it.

Signed-off-by: Tapasweni Pathak 
Signed-off-by: Greg Kroah-Hartman

Staging: comedi: range: remove unnecessary sanity check

2014-03-09T02:59:48+00:00

This check is unnecessary because range_table will always be
initialized to range_unknown by comedi_device_postconfig() for
drivers that do not initialize range_table or range_table_list

Signed-off-by: Fred Akers 
Reviewed-by: H Hartley Sweeten 
Reviewed-by: Ian Abbott 
Signed-off-by: Greg Kroah-Hartman

Staging: comedi: range: tidy up comedi_check_chanlist()

2014-03-09T02:59:48+00:00

Refactor this function to remove an extra indent level

Signed-off-by: Fred Akers 
Reviewed-by: H Hartley Sweeten 
Reviewed-by: Ian Abbott 
Signed-off-by: Greg Kroah-Hartman