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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 9/14/23 03:05, Wu, Wentong wrote:
>> From: Oliver Neukum <oneukum@suse.com>
>>
>> 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.

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