comedi: dmm32at: serialize use of paged registers

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commit e03b29b55f upstream.

Some of the hardware registers of the DMM-32-AT board are multiplexed,
using the least significant two bits of the Miscellaneous Control
register to select the function of registers at offsets 12 to 15:

 00 => 8254 timer/counter registers are accessible
 01 => 8255 digital I/O registers are accessible
 10 => Reserved
 11 => Calibration registers are accessible

The interrupt service routine (`dmm32at_isr()`) clobbers the bottom two
bits of the register with value 00, which would interfere with access to
the 8255 registers by the `dm32at_8255_io()` function (used for Comedi
instruction handling on the digital I/O subdevice).

Make use of the generic Comedi device spin-lock `dev->spinlock` (which
is otherwise unused by this driver) to serialize access to the
miscellaneous control register and paged registers.

Fixes: 3c501880ac ("Staging: comedi: add dmm32at driver")
Cc: stable@vger.kernel.org
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://patch.msgid.link/20260112162835.91688-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Ian Abbott 2026-01-12 16:28:35 +00:00 • committed by Greg Kroah-Hartman

parent 2501c49306

commit 169164fe51

1 changed files with 30 additions and 2 deletions

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drivers/comedi/drivers/dmm32at.c

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