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    SubjectRe: [PATCH v2 1/3] usb: gadget: storage: Add fsg_get_toc helper
    On 03/21/2011 04:20 PM, ext Alan Stern wrote:
    > On Mon, 21 Mar 2011, Roger Quadros wrote:
    >
    >> From: Roger Quadros<roger.quadros@nokia.com>
    >>
    >> fsg_get_toc can be used by both storage gadgets to build a CD-ROM
    >> Table of Contents which can be used as data for READ_TOC command.
    >> Currently fsg_get_toc supports two TOC formats, i.e.
    >> format 0: Formatted TOC and format 2: Raw TOC.
    >>
    >> Raw TOC is required for CD-ROM emulation to work with Mac OS-X.
    >>
    >> Signed-off-by: Roger Quadros<roger.quadros@nokia.com>
    >> ---
    >> drivers/usb/gadget/storage_common.c | 68 +++++++++++++++++++++++++++++++++++
    >> 1 files changed, 68 insertions(+), 0 deletions(-)
    >>
    >> diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
    >> index b015561..d47f148 100644
    >> --- a/drivers/usb/gadget/storage_common.c
    >> +++ b/drivers/usb/gadget/storage_common.c
    >> @@ -655,6 +655,74 @@ static void store_cdrom_address(u8 *dest, int msf, u32 addr)
    >> }
    >> }
    >>
    >> +/**
    >> + * fsg_get_toc() - Builds a TOC with required format @format.
    >> + * @curlun: The LUN for which the TOC has to be built
    >> + * @msf: Min Sec Frame format or LBA format for address
    >> + * @format: TOC format code
    >> + * @buf: The buffer into which the TOC is built
    >> + *
    >> + * Builds a Table of Content which can be used as data for READ_TOC command.
    >> + * The TOC simulates a single session, single track CD-ROM mode 1 disc.
    >> + *
    >> + * Returns number of bytes written to @buf, -EINVAL if format not supported.
    >> + */
    >> +static int fsg_get_toc(struct fsg_lun *curlun, int msf, int format, u8 *buf)
    >> +{
    >> + int i, len;
    >> + switch (format) {
    >> + case 0:
    >> + /* Formatted TOC */
    >> + len = 4 + 2*8; /* 4 byte header + 2 descriptors */
    >> + memset(buf, 0, len);
    >> + len -= 2; /* TOC Length excludes length field */
    >> + buf[1] = len; /* TOC data length */
    >
    > These two lines are wrong. You should do:
    >
    > buf[1] = len - 2; /* TOC data length excludes header */
    >
    > The way it is now, the function ends up returning 18 instead of 20,
    > causing the wrong amount of data to be transmitted.

    Yes indeed.

    >
    >> + buf[2] = 1; /* First track number */
    >> + buf[3] = 1; /* Last track number */
    >> + buf[5] = 0x16; /* Data track, copying allowed */
    >> + buf[6] = 0x01; /* Only track is number 1 */
    >> + store_cdrom_address(&buf[8], msf, 0);
    >> +
    >> + buf[13] = 0x16; /* Lead-out track is data */
    >> + buf[14] = 0xAA; /* Lead-out track number */
    >> + store_cdrom_address(&buf[16], msf, curlun->num_sectors);
    >> + return len;
    >> + break;
    >> +
    >> + case 2:
    >> + /* Raw TOC */
    >> + len = 4 + 3*11; /* 4 byte header + 3 descriptors */
    >> + memset(buf, 0, len); /* Header + A0, A1& A2 descriptors */
    >> + len -= 2; /* TOC Length excludes length field */
    >> + buf[1] = len; /* TOC data length */
    >
    > Same thing here. I'm surprised it worked during testing. Did you
    > really check to see that the correct data was being sent?

    I too am surprised. I tried playing a few videos without problems.
    After you pointed out the problem I ran a checksum on the files and they match!!

    But thanks for pointing out, I'll send a new patch.

    --
    regards,
    -roger


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