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	Tue, 28 Jul 2015 05:30:56 -0400
Subject: Re: [PATCH v4 1/1] usb: gadget: f_uac2: finalize wMaxPacketSize
 according to bandwidth
To: Peter Chen <peter.chen@freescale.com>, balbi@ti.com
References: <1438047504-19786-1-git-send-email-peter.chen@freescale.com>
Cc: linux-usb@vger.kernel.org, andrzej.p@samsung.com,
	Daniel Mack <zonque@gmail.com>, tiwai@suse.de,
	stable@vger.kernel.org, Alan Stern <stern@rowland.harvard.edu>
From: Daniel Mack <daniel@zonque.org>
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Date: Tue, 28 Jul 2015 11:30:53 +0200
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On 07/28/2015 03:38 AM, Peter Chen wrote:
> +static void set_ep_max_packet_size (struct f_uac2_opts *uac2_opts,
> +	struct usb_endpoint_descriptor *ep_desc, unsigned int factor)
> +{
> +	int chmask;
> +	int srate;
> +	int ssize;
> +	u16 max_packet_size;
> +
> +	if (ep_desc == &fs_epin_desc || ep_desc == &hs_epin_desc) {
> +		chmask = uac2_opts->p_chmask;	
> +		srate = uac2_opts->p_srate;
> +		ssize = uac2_opts->p_ssize;
> +	} else {
> +		WARN_ON (ep_desc != &fs_epout_desc && ep_desc != &hs_epout_desc);
> +		chmask = uac2_opts->c_chmask;
> +		srate = uac2_opts->c_srate;
> +		ssize = uac2_opts->c_ssize;
> +	}
> +
> +	max_packet_size = num_channels(chmask) * ssize *
> +	       	DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
> +	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
> +				ep_desc->wMaxPacketSize);
> +}

Thinking about it again, it would probably be nicer to make this
function return wMaxPacketSize directly:

  fs_epin_desc.wMaxPacketSize =
    calc_ep_max_packet_size(uac2_opts->p_chmask,
                            uac2_opts->p_srate,
                            uac2_opts->p_ssize,
                            1000);

  hs_epin_desc.wMaxPacketSize =
    calc_ep_max_packet_size(uac2_opts->p_chmask,
                            uac2_opts->p_srate,
                            uac2_opts->p_ssize,
                            8000);

  ...