Inaky Perez-Gonzalez <[EMAIL PROTECTED]> writes:
[...]
> Here is my point: it's way easier and more maintenable to do
>
> struct some_descriptor {
> __le16 foo;
> __u8 bar;
> } __attribute__((packed));
> ...
> struct some_descriptor descr;
> ...
> read_from_wire(&descr, sizeof(descr));
> do_something_with_values(&descr->foo, &descr->bar)
Out of curiosity, where endianness issues are handled in this code?
>
> than
>
> u8 buffer[SOME_DESCRIPTOR_DT_SIZE], foo;
> le16 bar;
> read_from_wire(buffer, SOME_DESCRIPTOR_DT_SIZE);
> bar = le16_to_cpu((__le16)buffer[1] << 8 | buffer[0]);
> foo = buffer[2];
> do_something_with_values(foo, bar)
This IMHO, could look, e.g., like this:
struct some_descriptor {
__u8 foo[2];
__u8 bar;
};
...
struct some_descriptor descr;
...
read_from_wire(&descr, sizeof(descr));
do_something_with_values(usb_get_uint16(descr->foo), bar);
...
usb_set_uint16(descr->foo, 2385);
where:
static inline unsigned usb_get_uint16(__u8 const *p)
{
return p[0] | (p[1] << 8);
}
static inline void usb_set_uint16(__u8 const *p, unsigned value)
{
p[0] = value;
p[1] = value >> 8;
}
Not only this avoids packed attribute, but makes it obvious that one
can't just use bare descr->foo in and endianness-safe way.
-- Sergei.
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