RE: [PATCH v16 1/4] usb: Add support for Intel LJCA device

["Wu, Wentong" <wentong.wu@xxxxxxxxx>]

> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> 
> Hi,
> 
> On 9/14/23 03:05, Wu, Wentong wrote:
> >> From: Oliver Neukum <oneukum@xxxxxxxx>
> >>
> >> On 13.09.23 03:40, Wentong Wu wrote:
> >>
> >>> +struct ljca_bank_descriptor {
> >>> +	u8 bank_id;
> >>> +	u8 pin_num;
> >>> +
> >>> +	/* 1 bit for each gpio, 1 means valid */
> >>> +	u32 valid_pins;
> >>
> >> No endianness?
> >
> > On both sides, the endianness is same.
> 
> Right, but normally USB drivers are also written so that they can work on big-
> endian CPUs.
> 
> I realize that this driver will likely never be used with a big-endian CPU but still it
> is good practice to make the driver work on big-endian CPUs too. Even if it is just
> to set a good example when other drivers copy the code.

Thanks, I agree the point here.

And I will update the driver after the test, thanks again.

BR,
Wentong
>
> 
> So this should be:
> 
> struct ljca_bank_descriptor {
> 	u8 bank_id;
> 	u8 pin_num;
> 
> 	/* 1 bit for each gpio, 1 means valid */
> 	__le32 valid_pins;
> } __packed;
> 
> And then when reading valid_pins you should use:
> 
> 	u32 valid_pins = get_unaligned_le32(&ljca_bank_descriptor.valid_pins);
> 
> On x86_64 the compiler should optimize all of this away to just a regular read.
> 
> Regards,
> 
> Hans