RE: [PATCH 1/3] mfd: Add realtek USB card reader driver

Roger Tseng
2014-01-08T07:56:05Z

Hi Dan,

>> +int rtsx_usb_ep0_write_register(struct rtsx_ucr *ucr, u16 addr,
>> + u8 mask, u8 data)
>> +{
>> + u16 value = 0, index = 0;
>> +
>> + value |= (u16)(3 & 0x03) << 14;
>> + value |= (u16)(addr & 0x3FFF);
>
>Don't do pointless things:
>
> value |= 0x03 << 14;
> value |= addr & 0x3FFF;
>
>> + value = ((value << 8) & 0xFF00) | ((value >> 8) & 0x00FF);
>
>This is an endian conversion? It is buggy. Use the kernel endian
>conversion functions cpu_to_le16().

This is not a conversion for endianess with respect to CPU but for command format of the device. It should always be performed regardless of platform.

In other words, it could be equivalent to:
value |= 0x03 << 6; // lower byte
value |= (addr & 0x3F00) >> 8; // lower byte
value |= (addr & 0xFF) << 8; //higher byte

We think the previous form is easier to read. Should we keep it or change to the later one?