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    SubjectRe: [PATCH 1/2] Input: i8042 - Prevent intermixing i8042 commands
    On Thu, Aug 27, 2020 at 10:52 PM Raul E Rangel <rrangel@chromium.org> wrote:
    >
    > The i8042_mutex must be held by writers of the AUX and KBD ports, as
    > well as users of i8042_command. There were a lot of users of
    > i8042_command that were not calling i8042_lock_chip/i8042_unlock_chip.
    > This resulted in i8042_commands being issues in between PS/2
    > transactions.
    >
    > This change moves the mutex lock into i8042_command and removes the
    > burden of locking the mutex from the callers.

    Which is wrong according to your very patch. See below.

    > It is expected that the i8042_mutex is locked before calling
    > i8042_aux_write or i8042_kbd_write. This is currently done by the PS/2
    > layer via ps2_begin_command and ps2_end_command. Other modules
    > (serio_raw) do not currently lock the mutex, so there is still a
    > possibility for intermixed commands.

    ...

    > + mutex_lock(&i8042_mutex);
    > +
    > spin_lock_irqsave(&i8042_lock, flags);
    > retval = __i8042_command(param, command);
    > spin_unlock_irqrestore(&i8042_lock, flags);
    >
    > + mutex_unlock(&i8042_mutex);

    Question 1. Why do you need mutex at all in the above situation? Spin
    lock isn't enough?

    ...

    > - i8042_lock_chip();
    > -
    > if (value == LED_OFF)
    > i8042_command(NULL, CLEVO_MAIL_LED_OFF);
    > else if (value <= LED_HALF)
    > i8042_command(NULL, CLEVO_MAIL_LED_BLINK_0_5HZ);
    > else
    > i8042_command(NULL, CLEVO_MAIL_LED_BLINK_1HZ);
    > -
    > - i8042_unlock_chip();
    > -

    Now, these three commands are not considered as a transaction (no
    atomicity). That's why your patch is wrong.

    > }

    ...

    > int rc;
    >
    > - i8042_lock_chip();
    > rc = i8042_command(&param, A1655_WIFI_COMMAND);
    > - i8042_unlock_chip();
    > return rc;

    rc become redundant.

    --
    With Best Regards,
    Andy Shevchenko

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