linux-kernel - Re: [PATCH v2] usb: gadget: f_midi: Add checking if it need align buffer's size to an ep's maxpacketsize

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Message-ID: <xa1t7fcswgjj.fsf@mina86.com>
Date:	Mon, 11 Jul 2016 13:38:40 +0200
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Baolin Wang <baolin.wang@...aro.org>, balbi@...nel.org
Cc:	gregkh@...uxfoundation.org, eu@...ipetonello.com,
	r.baldyga@...sung.com, dan.carpenter@...cle.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	broonie@...nel.org, baolin.wang@...aro.org
Subject: Re: [PATCH v2] usb: gadget: f_midi: Add checking if it need align buffer's size to an ep's maxpacketsize

On Mon, Jul 11 2016, Baolin Wang wrote:
> Some gadget device (such as dwc3 gadget) requires quirk_ep_out_aligned_size
> attribute, which means it need to align the request buffer's size to an ep's
> maxpacketsize.
>
> Thus we add usb_ep_align_maybe() function to check if it is need to align
> the request buffer's size to an ep's maxpacketsize.
>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> Acked-by: Michal Nazarewicz <mina86@...a86.com>
> ---
> Changelog since v1:
>  - Remove the in_ep modification.
>  - Remove max_t() function.
>
>  drivers/usb/gadget/function/f_midi.c |   12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> index 58fc199..59f6278 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -359,10 +359,14 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
>  
>  	/* allocate a bunch of read buffers and queue them all at once. */
>  	for (i = 0; i < midi->qlen && err == 0; i++) {
> -		struct usb_request *req =
> -			midi_alloc_ep_req(midi->out_ep,
> -				max_t(unsigned, midi->buflen,
> -					bulk_out_desc.wMaxPacketSize));
> +		struct usb_request *req;
> +		unsigned length;
> +
> +		length = midi->buflen < bulk_out_desc.wMaxPacketSize
> +			? bulk_out_desc.wMaxPacketSize
> +			: usb_ep_align_maybe(midi->gadget, midi->out_ep,
> +					     midi->buflen);

As pointed out by Felipe, the packet does not need to be wMaxPacketSize
so this can simply be:

> +		length = usb_ep_align_maybe(midi->gadget, midi->out_ep,
> +					    midi->buflen);

> +		req = midi_alloc_ep_req(midi->out_ep, length);
>  		if (req == NULL)
>  			return -ENOMEM;
>  
> -- 
> 1.7.9.5
>

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»