On Tue, Sep 17, 2019 at 10:43 PM Marek Vasut <marek.va...@gmail.com> wrote:
>
> Due to constant influx of more and more weird and broken USB sticks,
> do as Linux does in commit 779b457f66e10de3471479373463b27fd308dc85
>
> usb: storage: scsiglue: further describe our 240 sector limit
>
> Just so we have some sort of documentation as to why
> we limit our Mass Storage transfers to 240 sectors,
> let's update the comment to make clearer that
> devices were found that would choke with larger
> transfers.
>
> While at that, also make sure to clarify that other
> operating systems have similar, albeit different,
> limits on mass storage transfers.
>
> And reduce the maximum transfer length of USB storage to 120 kiB.
>
> Signed-off-by: Marek Vasut <marek.vasut+rene...@gmail.com>
> Cc: Bin Meng <bmeng...@gmail.com>
> Cc: Simon Glass <s...@chromium.org>
> ---
> V2: Reshuffle the code a bit, always clamp the transfer size to 240 blocks
> ---
> common/usb_storage.c | 43 ++++++++++++++++++++++---------------------
> 1 file changed, 22 insertions(+), 21 deletions(-)
>
> diff --git a/common/usb_storage.c b/common/usb_storage.c
> index 8c889bb1a6..e1b539a082 100644
> --- a/common/usb_storage.c
> +++ b/common/usb_storage.c
> @@ -938,31 +938,32 @@ do_retry:
> static void usb_stor_set_max_xfer_blk(struct usb_device *udev,
> struct us_data *us)
> {
> - unsigned short blk;
> - size_t __maybe_unused size;
> - int __maybe_unused ret;
> -
> -#if !CONFIG_IS_ENABLED(DM_USB)
> -#ifdef CONFIG_USB_EHCI_HCD
> /*
> - * The U-Boot EHCI driver can handle any transfer length as long as
> - * there is enough free heap space left, but the SCSI READ(10) and
> - * WRITE(10) commands are limited to 65535 blocks.
> + * Limit the total size of a transfer to 120 KB.
> + *
> + * Some devices are known to choke with anything larger. It seems like
> + * the problem stems from the fact that original IDE controllers had
> + * only an 8-bit register to hold the number of sectors in one
> transfer
> + * and even those couldn't handle a full 256 sectors.
> + *
> + * Because we want to make sure we interoperate with as many devices
> as
> + * possible, we will maintain a 240 sector transfer size limit for USB
> + * Mass Storage devices.
> + *
> + * Tests show that other operating have similar limits with Microsoft
> + * Windows 7 limiting transfers to 128 sectors for both USB2 and USB3
> + * and Apple Mac OS X 10.11 limiting transfers to 256 sectors for USB2
> + * and 2048 for USB3 devices.
> */
> - blk = USHRT_MAX;
> -#else
> - blk = 20;
> -#endif
> -#else
> + unsigned short blk = 240;
> +
> +#if CONFIG_IS_ENABLED(DM_USB)
> + size_t size;
> + int ret;
> +
> ret = usb_get_max_xfer_size(udev, (size_t *)&size);
> - if (ret < 0) {
> - /* unimplemented, let's use default 20 */
> - blk = 20;
> - } else {
> - if (size > USHRT_MAX * 512)
> - size = USHRT_MAX * 512;
> + if ((ret >= 0) && (size < 240 * 512))
size < blk * 512
> blk = size / 512;
> - }
> #endif
>
> us->max_xfer_blk = blk;
> --
Looks good otherwise
Reviewed-by: Bin Meng <bmeng...@gmail.com>
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