On Mon, 13 Mar 2006, Craig W. Nadler wrote:
> I've put together a patch demonstrating how Interface Association
> Descriptors could be supported with a minimal amount of changes the
> current USB stack. When a USB device is enumerated the descriptors are
> parsed by the code in drivers/usb/core/config.c. A list of IADs for a
> given configuration would be stored in the usb_host_config struct for
> that configuration. If an interface is referenced by an IAD then a
> pointer to the IAD will be stored in the usb_host_interface struct for
> that interface.
Some minor gammatical comments on the printer gadget patch: "it's" is a
contraction of "it is", whereas "its" is a possessive pronoun. Also,
"howto" should be two words ("how to") unless you're using it as a noun.
--- a/drivers/usb/core/config.c 2006-01-02 22:21:10.000000000 -0500
+++ b/drivers/usb/core/config.c 2006-03-05 01:19:33.000000000 -0500
@@ -310,6 +312,22 @@
++n;
}
+ } else if (header->bDescriptorType ==
+ USB_DT_INTERFACE_ASSOCIATION) {
+ if (iad_num == USB_MAXIADS) {
+ dev_err(ddev, "found more Interface "
+ "Association Descriptors "
+ "than allocated for\n");
+ } else {
+ config->intf_assoc[iad_num] = kzalloc(
+ header->bLength, GFP_KERNEL);
+ if (!config->intf_assoc[iad_num])
+ return -ENOMEM;
+ memcpy (config->intf_assoc[iad_num], header,
+ header->bLength);
+ iad_num++;
+ }
Unless you think that interface association descriptors are critical for
using the device correctly, you should accept allocation failures and
continue instead of aborting.
Furthermore, there's no real point in copying the descriptor to this
newly-allocated memory area. The original data bytes will remain
available in the raw_descriptors array, so it would be enough to have
config->intf_assoc[iad_num] be nothing more than a pointer into
raw_descriptors.
@@ -419,6 +437,10 @@
struct usb_host_config *cf = &dev->config[c];
kfree(cf->string);
+ for (i = 0; i < USB_MAXIADS; i++) {
+ if (cf->intf_assoc[i])
+ kfree(cf->intf_assoc[i]);
+ }
The test isn't needed. Of course, if you change intf_assoc[i] to be a
pointer into raw_descriptors then the kfree and the loop aren't needed
either.
Alan Stern
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