On 07/03/17 18:13, Cheah Kok Cheong wrote:
If comedi module is loaded with the following max allowed parameter
[comedi_num_legacy_minors=48], subsequent loading of an auto-configured
device will fail at auto-configuration. If there's no fall back in
place then module loading will fail.
In this case, a default to auto-configure comedi_test module failed
to auto-configure with the following messages. It loaded but fell back
to unconfigured mode.
comedi_test comedi_testd: ran out of minor numbers for board device files
comedi_test comedi_testd: driver 'comedi_test' could not create device.
comedi_test: unable to auto-configure device
This is due to changes in commit 38b9722a4414
("staging: comedi: avoid releasing legacy minors automatically") which
will not allocate a minor number when comedi_num_legacy_minors equals
COMEDI_NUM_BOARD_MINORS. COMEDI_NUM_BOARD_MINORS is defined to be
0x30 which is 48.
Sorry, I don't consider this to be a bug. The number of minor device
numbers available for auto-configured devices is 48 minus
comedi_num_legacy_minors. Using up all available minor device numbers
is a useful test case for running out of minor device numbers, although
this relies on knowing the limit is 48. Perhaps the description of the
module parameter could be improved to mention the limits, as could the
error message when running out of minor device numbers.
Commit 38b9722a4414 is irrelevant here. Prior to that commit, the first
'comedi_num_legacy_minors' minor numbers were still allocated to legacy
devices created during module initialization, leaving 48 minus
comedi_num_legacy_minors minors (possibly none) available for
auto-configured devices.
This goes for a simple fix which limit comedi_num_legacy_minors to 47
instead of tinkering with comedi_alloc_board_minor() and
comedi_release_hardware_device().
Fix: commit 38b9722a4414 ("staging: comedi: avoid releasing legacy minors
automatically")
Signed-off-by: Cheah Kok Cheong <thrus...@gmail.com>
---
V2:
-Amend commit log to specify that comedi_test module failed
to auto-configure and fell back to unconfigured mode.
For other devices with no fall back, module loading will fail.
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbo...@mev.co.uk> )=-
-=( Web: http://www.mev.co.uk/ )=-
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