Re: [PATCH 1/2] ide: Add tx4939ide driver

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello, I wrote:

>>>>>   This doesn't look consistent (aside from the TX4939IDE_REG8/16 
>>>>> issue) -- mm_outsw_swap() calls cpu_to_le16() before writing 
>>>>> 16-bit data but this code doesn't. So, either one of those should 
>>>>> be wrong...
>>>>
>>>> Thanks, this code should be wrong.  IDE_TFLAG_OUT_DATA is totally
>>>> untested...
>>>
>>>   Hum, not necessarily...
>>>   If the data register is BE, this should work correctly, if I don't 
>>> mistake (once you fix the data register's address).
>
>> Hmm... or ide_tf_load()/ide_tf_read() is broken for big endian MIPS ?
>> (and possibly SPARC etc.)
>
>> __ide_mm_writesw(port, &data, 1) should be used instead of writew()
>> for IDE_TFLAG_OUT_DATA?
>
>    Probably the code there relies on the writew() doing the necessary 
> byte swapping -- the same as ata_{in|out}_data() must be reying on 
> ins[wl]() and outs[wl]() to do that, as well as on 
> __ide_mm_reads[wl]() and __ide_mm_writes[wl]() -- which boil down to 
> reads[wl]() and writes[wl]() on MIPS.
>    What's not clear to me is why in MIPS read[wlq]() vs reads[wlq](), 
> write[wlq]() vs writes[wl], in[wlq]() vs ins[wlq](), and out[wlq]() vs 
> outs[wlq]() are using the different byte swapping: the single form 
> uses ioswab[wlq]() while the sting form uses __mem_ioswab[wlq]() -- 
> and those are defined as one swapping bytes and the other not in 
> incluse/asm-mips/mach-generic/mangle-port.h. Cananybody shed some 
> light on this?

   Oh, I think I understand: the "single" versions take/return the value 
in host endian but the "string" version must treat the data as a stream 
of bytes.

MBR, Sergei