Re: [PATCH] missing NULL check in drivers/char/n_tty.c

From: Paul Fulghum (paulkf_at_microgate.com)
Date: 06/21/04

  • Next message: Stephen C. Tweedie: "Re: [2.4] page->buffers vanished in journal_try_to_free_buffers()" 
    Date:	Mon, 21 Jun 2004 10:06:46 -0500
To: Dan Aloni <da-x@colinux.org>

    Dan Aloni wrote:
    > Andrew Morton wrote:
    > I did a quick grep and it appears that all drivers have set ->chars_in_buffer().
    >
    > I suspect there are no drivers which fail to set chars_in_buffer.
    > Otherwise normal_poll() would have been oopsing in 2.4, 2.5 and 2.6?

    An addition should be made to include/linux/tty_driver.h
    to document the chars_in_buffer member of struct tty_driver
    and struct tty_operations as a required function.
    Currently, the documentation section of this header
    does not mention chars_in_buffer.

    Related issue:

    In looking at this, I noticed struct tty_ldisc
    (include/linux/tty_ldisc.h) defines and documents
    an optional (optional == NULL) member chars_in_buffer.
    N_TTY (drivers/char/n_tty.c) is the only line discipline
    that implements this member.

    drivers/char/pty.c is the only driver that
    uses ldisc.chars_in_buffer, and it checks for
    ldisc.chars_in_buffer == NULL before calling.

    13 other drivers call ldisc.chars_in_buffer without checking
    for ldisc.chars_in_buffer == NULL, but only inside conditional
    compilation for debug output. The value is not used, only logged.
    These conditional debug items look like cut and paste from
    one serial driver to another, and I doubt
    they have been recently used (or used at all).

    Which would be better?
    1. Ignore this
    2. Fix conditional debug output to check
        for ldisc.chars_in_buffer==NULL
    3. Remove conditional debug output 

    --
Paul Fulghum
paulkf@microgate.com
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  • Next message: Stephen C. Tweedie: "Re: [2.4] page->buffers vanished in journal_try_to_free_buffers()"

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