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SubjectRe: [PATCH v3 2/3] usb: ffs: check quirk to pad epout buf size when not aligned to maxpacketsize
On Wed, 30 Oct 2013, David Cohen wrote:

> Check gadget.quirk_ep_out_aligned_size to decide if buffer size requires
> to be aligned to maxpacketsize of an out endpoint. ffs_epfile_io() needs
> to pad epout buffer to match above condition if quirk is found.
>
> Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
> ---
> drivers/usb/gadget/f_fs.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
> index 75e4b78..b49dd55 100644
> --- a/drivers/usb/gadget/f_fs.c
> +++ b/drivers/usb/gadget/f_fs.c
> @@ -755,10 +755,12 @@ static ssize_t ffs_epfile_io(struct file *file,
> char __user *buf, size_t len, int read)
> {
> struct ffs_epfile *epfile = file->private_data;
> + struct usb_gadget *gadget = epfile->ffs->gadget;
> struct ffs_ep *ep;
> char *data = NULL;
> ssize_t ret;
> int halt;
> + size_t orig_len = len;
>
> goto first_try;
> do {
> @@ -794,6 +796,21 @@ first_try:
> goto error;
> }
>
> + /*
> + * Controller requires buffer size to be aligned to
> + * maxpacketsize of an out endpoint.
> + */
> + if (gadget->quirk_ep_out_aligned_size && read &&
> + !IS_ALIGNED(len, ep->ep->desc->wMaxPacketSize)) {

IS_ALIGNED works only when the second argument is a power of 2.

Interrupt endpoints are not required to have maxpacket sizes that are
powers of 2. Does this code ever get used for an interrupt endpoint?

> + size_t old_len = len;

Why add old_len here when you added orig_len above?

> + len = roundup(orig_len,
> + (size_t)ep->ep->desc->wMaxPacketSize);
> + if (unlikely(data) && len > old_len) {

If the original value wasn't aligned, how can len fail to be > old_len?

> + kfree(data);
> + data = NULL;
> + }
> + }
> +
> /* Allocate & copy */
> if (!halt && !data) {
> data = kzalloc(len, GFP_KERNEL);

Alan Stern



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