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    SubjectRe: [PATCH repost 3] [SCSI] Retrieve the Caching mode page
    On Mon, Nov 22, 2010 at 12:02:26PM -0800, Luben Tuikov wrote:
    > --- On Mon, 11/22/10, Linus Torvalds <torvalds@linux-foundation.org>
    > wrote:
    > > So I don't mind the patch per se, but I think it's potentially way more
    > > dangerous than it looks.
    >
    > This patch does not ask for pages that Windows doesn't ask for. The sd
    > driver already asks for all pages (page code 0x3F) and then checks if the
    > device is write protected. Here is the present code:
    >
    > 2217 sd_read_write_protect_flag(sdkp, buffer); 2218
    > sd_read_cache_type(sdkp, buffer); 2219
    > sd_read_app_tag_own(sdkp, buffer);
    >
    > Line 2217 asks for page code 0x3F, meaning all mode pages. Line 2218
    > asks for the Caching mode page or not at all if the device flags forbid
    > it (all USB storage devices in the Linux kernel).
    >
    > This patch adds processing of the data returned when all mode pages are
    > asked for (0x3F) in the function on line 2218. It then parses the data to
    > find out if the Caching mode page is present.

    As long as you are not changing the command stream that the devices see, I
    think this is a reasonable risk to take.

    What are the consequences if the device returns what appear to be a Caching
    Mode Page, but it is actually filled with garbage or otherwise inaccurate
    data?

    Matt

    --
    Matthew Dharm Home: mdharm-usb@one-eyed-alien.net
    Maintainer, Linux USB Mass Storage Driver

    You suck Stef.
    -- Greg
    User Friendly, 11/29/97
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