On Monday 16 October 2006 06:55, pradeep singh wrote:
> Hi all
> I was reading the sample code for usb-skeleton.c and i need to clear
> somethings.
>
> 1. in skel_probe()
> 247 struct usb_skel *dev = NULL;
> ...
> 254 /* allocate memory for our device state and initialize it */
> 255 dev = kmalloc(sizeof(*dev), GFP_KERNEL);
> 256 if (dev == NULL) {
> 257 err("Out of memory");
> 258 goto error;
> 259 }
> ...
>
> struct usb_skel *dev = NULL on line no. 247 but when we allocate
> memory for it we didnt use it like
> dev = kmalloc(sizeof(struct usb_skel), GFP_KERNEL)
> instead we are using kmalloc(sizeof(*dev), GFP_KERNEL). Had it been
> allocated initially and then using *dev somewhere is understandable.
> but using *dev before allocating dev seems weird.
sizeof(*dev) doesn't really dereference dev. It just returns the
size of whatever dev would point to.
> 2. What does le16_to_cpu(...) does?
Converts a 2-byte (16-bit) number in little-endian to whatever
byte order the CPU uses.
> Is it necessary to use it here?
> 278 buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
> What is the significance of it. Tried going through source but couldnt
> make out much.
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