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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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