linux-kernel - Re: [PATCH 2/2] check quirk to pad epout buf size when not aligned to maxpacketsize

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Date:	Sun, 10 Nov 2013 20:01:00 -0800
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	Michal Nazarewicz <mpn@...gle.com>
CC:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, Michal Nazarewicz <mina86@...a86.com>
Subject: Re: [PATCH 2/2] check quirk to pad epout buf size when not aligned
 to maxpacketsize

Hi Michal,

On 11/10/2013 08:50 AM, Michal Nazarewicz wrote:
> From: Michal Nazarewicz <mina86@...a86.com>
> 
> 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: Michal Nazarewicz <mina86@...a86.com>
> ---
>  I'm wondering whether the len should be aligned down rather then up.
>  This would have it's own problems, but maybe better then
>  a possibility of silently dropping data.
> 
>  drivers/usb/gadget/f_fs.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
> index f875f26..ea0b8ba 100644
> --- a/drivers/usb/gadget/f_fs.c
> +++ b/drivers/usb/gadget/f_fs.c
> @@ -753,8 +753,9 @@ 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;
> -	ssize_t ret;
> +	ssize_t ret, data_len;
>  	char *data;
>  	int halt;
>  
> @@ -787,6 +788,13 @@ static ssize_t ffs_epfile_io(struct file *file,
>  
>  	/* Allocate & copy */
>  	if (!halt) {
> +		/*
> +		 * Controller requires buffer size to be aligned to
> +		 * maxpacketsize of an out endpoint.
> +		 */
> +		data_len = read && gadget->quirk_ep_out_aligned_size ?
> +			usb_ep_align_maxpacketsize(ep->ep, len) : len;
> +
>  		data = kmalloc(len, GFP_KERNEL);

Shouldn't this kmalloc() allocate 'data_len' bytes, instead of 'len'?

Br, David
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