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    SubjectRe: [PATCH v2 1/3] usb: gadget: storage: Add fsg_get_toc helper
    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.

    > + 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?

    Alan Stern



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