[U-Boot] [PATCH 1/2] mmc: add bcm2835 driver

[Vikram Narayanan <vikram186@gmail.com>]

On 10/28/2012 8:58 AM, Stephen Warren wrote:
> On 10/26/2012 05:33 AM, Vikram Narayanan wrote:
>> Some nitpicks.
>>
>> On 10/24/2012 10:20 AM, Stephen Warren wrote:
<snip>
>>> +static u8 bcm2835_sdhci_readb(struct sdhci_host *host, int reg)
>>> +{
>>> +    u32 val = bcm2835_sdhci_raw_readl(host, (reg&   ~3));
>>> +    val = val>>   (reg<<   3&   0x18)&   0xff;
>>> +
>>> +    return (u8)val;
>>> +}
>>
>> Can the above used magics be made as macros?
>
> This code was taken directly from the downstream Linux kernel, so I
> changed it as little as possible, to make comparisons easier. Still, if
> people want I can certainly make it easier to understand the expression
> a bit.

Seems reasonable.

> I don't think the issue is the magic numbers so much as understanding
> what the expression does; the magic are obvious then. It's simply
> extracting byte n from from a u32. Would the following be more obvious:
>
> byte_num = reg&  3;
> byte_shift = bytenum * 8;
> byte = (val>>  byte_shift)&  0xff;
>
> ... and similar for the other functions?

This looks better to me than the former. Thanks.

~Vikram