Re: [PATCH 5/5 v5] usb:gadget: Add SuperSpeed support to theGadget Framework

[Felipe Balbi]

Hi,

On Wed, Mar 23, 2011 at 10:04:57AM +0200, Tatyana Brokhman wrote:
> This patch adds the SuperSpeed functionality to the gadget framework.
> In order not to force all the gadget drivers to supply SuperSpeed
> descriptors when operating in SuperSpeed mode the following approach was
> taken:
> If we're operating in SuperSpeed mode and the gadget driver didn't supply
> SuperSpeed descriptors, the composite layer will automatically create
> SuperSpeed descriptors with default values.
> Support for new SuperSpeed BOS descriptor was added.
> Support for SET_FEATURE and GET_STATUS requests in SuperSpeed mode was
> added.

IMHO, this patch tries to do too much in one huge patch. It needs major
splitting.

Also, I don't get why you decided to go the path of letting composite.c
generate the super speed descriptors instead of expecting gadget drivers
to pass those should they support super speed.

I would like the other way much better: first, it's what we already do
for full/low speed and high speed. Second, we can easily see the
descriptors by opening the gadget driver's code.

There are a few more comments below, but this patch needs major, major
splitting.

> Signed-off-by: Tatyana Brokhman <tlinder@xxxxxxxxxxxxxx>

missing the tear line --- here

> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index fb7e488..d5fe1c2 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -73,6 +73,123 @@ MODULE_PARM_DESC(iSerialNumber, "SerialNumber string");
>  
>  static char composite_manufacturer[50];
>  
> +/* Default endpoint companion descriptor */
> +static struct usb_ss_ep_comp_descriptor default_ep_comp_desc = {
> +		.bDescriptorType = USB_DT_SS_ENDPOINT_COMP,
> +		.bLength = 0x06,

there's a define for this:

#define USB_DT_SS_EP_COMP_SIZE		6

> +/**
> + * create_ss_descriptors() - Generate SuperSpeed descriptors
> + * with default values
> + * @f: pointer to usb_function to generate the descriptors for
> + *
> + * This function receives a pointer to usb_function and adds
> + * missing super speed descriptors in the ss_descriptor field
> + * according to its hs_descriptors field.
> + *
> + * This function copies f->hs_descriptors while updating the
> + * endpoint descriptor and adding endpoint companion descriptor.
> + */
> +static void create_ss_descriptors(struct usb_function *f)
> +{
> +	unsigned bytes;		/* number of bytes to allocate */
> +	unsigned n_desc;	/* number of descriptors */
> +	void *mem;		/* allocated memory to copy to */
> +	struct usb_descriptor_header **tmp;
> +	struct usb_endpoint_descriptor	*ep_desc ;
> +	struct usb_ss_ep_comp_descriptor *ep_comp_desc;
> +	struct usb_descriptor_header **src = f->hs_descriptors;
> +
> +	if (!f->hs_descriptors)
> +		return;
> +
> +	/*
> +	 * Count number of EPs (in order to know how many SS_EP_COMPANION
> +	 * descriptors to add), the total number of descriptors and the sum of
> +	 * each descriptor bLength field in order to know how much memory to
> +	 * allocate.
> +	 */
> +	for (bytes = 0, n_desc = 0, tmp = src; *tmp; tmp++, n_desc++) {
> +		if ((*tmp)->bDescriptorType == USB_DT_ENDPOINT) {
> +			bytes += default_ep_comp_desc.bLength;
> +			n_desc++;
> +		}
> +		bytes += (*tmp)->bLength;
> +	}
> +
> +	bytes += (n_desc + 1) * sizeof(*tmp);
> +	mem = kmalloc(bytes, GFP_KERNEL);
> +	if (!mem)
> +		return;
> +
> +	/*
> +	 * Fill in pointers starting at "tmp", to descriptors copied starting
> +	 * at "mem" and return "ret"
> +	 */
> +	tmp = mem;
> +	f->ss_descriptors  = mem;
> +	mem += (n_desc + 1) * sizeof(*tmp);
> +	while (*src) {
> +		/* Copy the original descriptor */
> +		memcpy(mem, *src, (*src)->bLength);
> +		switch ((*src)->bDescriptorType) {
> +		case USB_DT_ENDPOINT:
> +			/* update ep descriptor */
> +			ep_desc = (struct usb_endpoint_descriptor *)mem;
> +			switch (ep_desc->bmAttributes &
> +				USB_ENDPOINT_XFERTYPE_MASK) {
> +			case USB_ENDPOINT_XFER_CONTROL:
> +				ep_desc->wMaxPacketSize = cpu_to_le16(512);
> +				ep_desc->bInterval = 0;
> +				break;
> +			case USB_ENDPOINT_XFER_BULK:
> +				ep_desc->wMaxPacketSize = cpu_to_le16(1024);
> +				ep_desc->bInterval = 0;
> +				break;
> +			case USB_ENDPOINT_XFER_INT:
> +			case USB_ENDPOINT_XFER_ISOC:
> +				break;
> +			}
> +			*tmp = mem;
> +			tmp++;
> +			mem += (*src)->bLength;
> +			/* add ep companion descriptor */
> +			memcpy(mem, &default_ep_comp_desc,
> +			       default_ep_comp_desc.bLength);
> +			*tmp = mem;
> +			tmp++;
> +			/* Update wBytesPerInterval for periodic endpoints */
> +			ep_comp_desc = (struct usb_ss_ep_comp_descriptor *)mem;
> +			switch (ep_desc->bmAttributes &
> +				USB_ENDPOINT_XFERTYPE_MASK) {
> +			case USB_ENDPOINT_XFER_INT:
> +			case USB_ENDPOINT_XFER_ISOC:
> +				ep_comp_desc->wBytesPerInterval =
> +					ep_desc->wMaxPacketSize;
> +				break;
> +			}
> +			mem += default_ep_comp_desc.bLength;
> +			break;
> +		default:
> +			*tmp = mem;
> +			tmp++;
> +			mem += (*src)->bLength;
> +			break;
> +		}
> +		src++;
> +	}
> +	/*
> +	 * The last (struct usb_descriptor_header *) in the descriptors
> +	 * vector is NULL
> +	 */
> +	*tmp = NULL;
> +	f->ss_desc_allocated = true;
> +}

I would rather expect gadget drivers to provide their own descriptors
just like we do for full/low speed and high speed descriptors. Why you
decided to take this approach ?

> +
>  /*-------------------------------------------------------------------------*/
>  /**
>   * next_ep_desc() - advance to the next EP descriptor
> @@ -118,6 +235,9 @@ int config_ep_by_speed(struct usb_gadget *g,
>  	struct usb_endpoint_descriptor *chosen_desc = NULL;
>  	struct usb_descriptor_header **speed_desc = NULL;
>  
> +	struct usb_ss_ep_comp_descriptor *comp_desc = NULL;
> +	int want_comp_desc = 0;
> +
>  	struct usb_descriptor_header **d_spd; /* cursor for speed desc */
>  
>  	if (!g || !f || !_ep)
> @@ -125,6 +245,13 @@ int config_ep_by_speed(struct usb_gadget *g,
>  
>  	/* select desired speed */
>  	switch (g->speed) {
> +	case USB_SPEED_SUPER:
> +		if (gadget_is_superspeed(g)) {
> +			speed_desc = f->ss_descriptors;
> +			want_comp_desc = 1;
> +			break;
> +		}

same here, I would expect gadget drivers to be changed providing the
correct descriptors. Just like I did when I sent my version.

In my opinion, it would be easier that way. We could see the descriptors
just by opening the gadget driver code. Besides, different gadget
drivers might want different "sane defaults".

>  	INFO(cdev, "%s speed config #%d: %s\n",
>  		({ char *speed;
>  		switch (gadget->speed) {
> -		case USB_SPEED_LOW:	speed = "low"; break;
> -		case USB_SPEED_FULL:	speed = "full"; break;
> -		case USB_SPEED_HIGH:	speed = "high"; break;
> +		case USB_SPEED_LOW:
> +			speed = "low";
> +			break;
> +		case USB_SPEED_FULL:
> +			speed = "full";
> +			break;
> +		case USB_SPEED_HIGH:
> +			speed = "high";
> +			break;
> +		case USB_SPEED_SUPER:
> +			speed = "super";
> +			break;
>  		default:		speed = "?"; break;
>  		} ; speed; }), number, c ? c->label : "unconfigured");

this part isn't part of this patch.

-- 
balbi
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