linux-kernel - Re: [PATCH v5 2/5] usb: gadget: add quirk_ep_out_aligned_size field to struct usb

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Date:	Tue, 12 Nov 2013 00:55:22 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	David Cohen <david.a.cohen@...ux.intel.com>, balbi@...com,
	gregkh@...uxfoundation.org
Cc:	stern@...land.harvard.edu, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	David Cohen <david.a.cohen@...ux.intel.com>
Subject: Re: [PATCH v5 2/5] usb: gadget: add quirk_ep_out_aligned_size field to struct usb_gadget

On Mon, Nov 11 2013, David Cohen wrote:
> Due to USB controllers may have different restrictions, usb gadget layer
> needs to provide a generic way to inform gadget functions to complain
> with non-standard requirements.
>
> This patch adds 'quirk_ep_out_aligned_size' field to struct usb_gadget
> to inform when controller's epout requires buffer size to be aligned to
> MaxPacketSize. A helper is also provided to align buffer size when
> necessary.
>
> Signed-off-by: David Cohen <david.a.cohen@...ux.intel.com>
> Acked-by: Alan Stern <stern@...land.harvard.edu>

Acked-by: Michal Nazarewicz <mina86@...a86.com>

> ---
>
> Michal,
>
> I added prefix 'usb: f_fs: ' to patch's subject. I did not add 'usb: gadget:
> f_fs' due to it would be too long.
>
>
>  include/linux/usb/gadget.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 23b3bfd0a842..41e8834af57d 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -441,6 +441,19 @@ static inline void usb_ep_fifo_flush(struct usb_ep *ep)
>  		ep->ops->fifo_flush(ep);
>  }
>  
> +/**
> + * usb_ep_align_maxpacketsize - returns @len aligned to ep's maxpacketsize
> + * @ep: the endpoint whose maxpacketsize is used to align @len
> + * @len: buffer size's length to align to @ep's maxpacketsize
> + *
> + * This helper is used in case it's required for any reason to align buffer's
> + * size to an ep's maxpacketsize.
> + */
> +static inline size_t usb_ep_align_maxpacketsize(struct usb_ep *ep, size_t len)
> +{
> +	return round_up(len, (size_t)ep->desc->wMaxPacketSize);
> +}
> +

Come to think of it, perhaps even better helper would be:

static inline size_t usb_ep_align_maybe(
	struct usb_gadget *gadget, struct usb_ep *ep, size_t len) {
	return gadget->quir_ep_out_aligned_size ?
		round_up(len, (size_t)ep->desc->wMaxPacketSize) : len;
}

>  
>  /*-------------------------------------------------------------------------*/
>  
> @@ -502,6 +515,8 @@ struct usb_gadget_ops {
>   *	only supports HNP on a different root port.
>   * @b_hnp_enable: OTG device feature flag, indicating that the A-Host
>   *	enabled HNP support.
> + * @quirk_ep_out_aligned_size: epout requires buffer size to be aligned to
> + *	MaxPacketSize.
>   *
>   * Gadgets have a mostly-portable "gadget driver" implementing device
>   * functions, handling all usb configurations and interfaces.  Gadget
> @@ -541,6 +556,7 @@ struct usb_gadget {
>  	unsigned			b_hnp_enable:1;
>  	unsigned			a_hnp_support:1;
>  	unsigned			a_alt_hnp_support:1;
> +	unsigned			quirk_ep_out_aligned_size:1;
>  };
>  #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
>  
> -- 
> 1.8.4.rc3
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--


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