https://github.com/torvalds/linux
Revision c284979affcc6870a9a6545fc4b1adb3816dfcbf authored by Benjamin Tissoires on 31 January 2013, 16:50:02 UTC, committed by Jiri Kosina on 31 January 2013, 16:57:53 UTC
i2c_hid_output_raw_report is used by hidraw to forward set_report requests. The current implementation of i2c_hid_set_report needs to take the report_id as an argument. The report_id is stored in the first byte of the buffer in argument of i2c_hid_output_raw_report. Not removing the report_id from the given buffer adds this byte 2 times in the command, leading to a non working command. Reported-by: Andrew Duggan <aduggan@synaptics.com> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
1 parent 320cde1
Tip revision: c284979affcc6870a9a6545fc4b1adb3816dfcbf authored by Benjamin Tissoires on 31 January 2013, 16:50:02 UTC
HID: i2c-hid: fix i2c_hid_output_raw_report
HID: i2c-hid: fix i2c_hid_output_raw_report
Tip revision: c284979
io_ordering.txt
On some platforms, so-called memory-mapped I/O is weakly ordered. On such
platforms, driver writers are responsible for ensuring that I/O writes to
memory-mapped addresses on their device arrive in the order intended. This is
typically done by reading a 'safe' device or bridge register, causing the I/O
chipset to flush pending writes to the device before any reads are posted. A
driver would usually use this technique immediately prior to the exit of a
critical section of code protected by spinlocks. This would ensure that
subsequent writes to I/O space arrived only after all prior writes (much like a
memory barrier op, mb(), only with respect to I/O).
A more concrete example from a hypothetical device driver:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
...
In the case above, the device may receive newval2 before it receives newval,
which could cause problems. Fixing it is easy enough though:
...
CPU A: spin_lock_irqsave(&dev_lock, flags)
CPU A: val = readl(my_status);
CPU A: ...
CPU A: writel(newval, ring_ptr);
CPU A: (void)readl(safe_register); /* maybe a config register? */
CPU A: spin_unlock_irqrestore(&dev_lock, flags)
...
CPU B: spin_lock_irqsave(&dev_lock, flags)
CPU B: val = readl(my_status);
CPU B: ...
CPU B: writel(newval2, ring_ptr);
CPU B: (void)readl(safe_register); /* maybe a config register? */
CPU B: spin_unlock_irqrestore(&dev_lock, flags)
Here, the reads from safe_register will cause the I/O chipset to flush any
pending writes before actually posting the read to the chipset, preventing
possible data corruption.
Computing file changes ...