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Message-ID: <Pine.LNX.4.44L0.1311050950260.1360-100000@iolanthe.rowland.org>
Date: Tue, 5 Nov 2013 09:52:54 -0500 (EST)
From: Alan Stern <stern@...land.harvard.edu>
To: David Cohen <david.a.cohen@...ux.intel.com>
cc: balbi@...com, <gregkh@...uxfoundation.org>,
<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/4] usb: ffs: check quirk to pad epout buf size when
not aligned to maxpacketsize
On Mon, 4 Nov 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@...ux.intel.com>
> ---
> drivers/usb/gadget/f_fs.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
> index 75e4b7846a8d..e7c3c3119552 100644
> --- a/drivers/usb/gadget/f_fs.c
> +++ b/drivers/usb/gadget/f_fs.c
> @@ -755,10 +755,13 @@ 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;
> + size_t data_len = 0;
> ssize_t ret;
> int halt;
> + size_t orig_len = len;
>
> goto first_try;
> do {
> @@ -794,11 +797,30 @@ 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) {
> + /*
> + * We pass 'orig_len' to usp_ep_align_maxpacketsize()
> + * due to we're in a loop and 'len' may have been
> + * changed.
> + */
> + len = usb_ep_align_maxpacketsize(ep->ep, orig_len);
> + if (data && len > data_len) {
> + kfree(data);
> + data = NULL;
> + data_len = 0;
> + }
> + }
Since the value of orig_len never changes, there's no point calling
usb_ep_align_maxpacketsize() inside the loop. You should call it only
once, before the loop starts. Once you do that, you won't need
orig_len at all.
Alan Stern
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