[alsa-devel] [PATCH 1/1] Allow any MIDI endpoint to drive use of interrupt transfer on Roland devices

[Takashi Iwai]

On Sat, 10 Oct 2015 20:59:01 +0200,
maillist at superlative.org wrote:
> 
> From: "Keith A. Milner" <kamilner at superlative.org>
> 
> Signed-off-by: Keith A. Milner <maillist at superlative.org>

The most important piece is missing -- why this change is needed at
all.  Could you give more detailed description?


thanks,

Takashi

> 
> diff --git a/sound/usb/midi.c b/sound/usb/midi.c
> index b901f46..52b8c72 100644
> --- a/sound/usb/midi.c
> +++ b/sound/usb/midi.c
> @@ -1860,9 +1860,14 @@ static void snd_usbmidi_switch_roland_altsetting(struct snd_usb_midi* umidi)
>  
>  	hostif = &intf->altsetting[1];
>  	intfd = get_iface_desc(hostif);
> +	/* If either or both of the endpoints support interrupt transfer,
> +	 * then use the alternate setting
> +	 */
>  	if (intfd->bNumEndpoints != 2 ||
> -	    (get_endpoint(hostif, 0)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != USB_ENDPOINT_XFER_BULK ||
> -	    (get_endpoint(hostif, 1)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != USB_ENDPOINT_XFER_INT)
> +	    !((get_endpoint(hostif, 0)->bmAttributes
> +	      & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT ||
> +	    (get_endpoint(hostif, 1)->bmAttributes
> +	      & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT))
>  		return;
>  
>  	snd_printdd(KERN_INFO "switching to altsetting %d with int ep\n",
> -- 
> 1.9.1
>