linux-kernel - Re: [PATCHv2 2/2] check quirk to pad epout buf size when not aligned to maxpacketsize

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Date:	Mon, 11 Nov 2013 15:15:45 -0800
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	Michal Nazarewicz <mina86@...a86.com>
CC:	Alan Stern <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/2] check quirk to pad epout buf size when not aligned
 to maxpacketsize

On 11/11/2013 03:21 AM, Michal Nazarewicz 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: Michal Nazarewicz <mina86@...a86.com>
> ---
>   drivers/usb/gadget/f_fs.c | 23 +++++++++++++++++++----
>   1 file changed, 19 insertions(+), 4 deletions(-)
>
>> On 11/10/2013 08:50 AM, Michal Nazarewicz wrote:
>>> @@ -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);
>
> On Mon, Nov 11 2013, David Cohen <david.a.cohen@...ux.intel.com> wrote:
>> Shouldn't this kmalloc() allocate 'data_len' bytes, instead of 'len'?
>
> Yes, of coures.
>
> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
> index e496b72..fd769a8 100644
> --- a/drivers/usb/gadget/f_fs.c
> +++ b/drivers/usb/gadget/f_fs.c

[snip]

>   			ret = ep->status;
>   			if (read && ret > 0 &&
> -			    unlikely(copy_to_user(buf, data, ret)))
> +			    unlikely(copy_to_user(buf, data, min(ret, len))))

You need to replace min(ret, len) by min_t(size_t, ret, len) to avoid
this warning:
drivers/usb/gadget/f_fs.c:858:124: warning: comparison of distinct 
pointer types lacks a cast [enabled by default]

Once again, you (or me) need to reply to my v5 patch set.

Br, David
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