Re: [PATCH, 1/2] mtd: m25p80: Let m25p80_read() fallback to spi transfer

[Marek Vasut <marex@denx.de>]

On 01/24/2017 12:41 AM, Kamal Dasu wrote:
> "ret can never be > 0 , it is only 0 or negative "
> 
> I can fix this.
> 
>>>> This looks really fragile and special-casing EINVAL here doesn't scale.
>>>> But still, if your controller driver is buggy, fix the driver, do not
>>>> pollute core code with workarounds. If you do support this sort of
>>>> accelerated read and it fails, it means something is seriously wrong.
>>>> If you need to invoke regular SPI reads to complete under some obscure
>>>> circumstances, do it from the driver, not here.
>>>
>>> I guess the other half of m25p80_read can be factored out and used as
>>> fallback from either m25p80_read or the controller driver.
>>
>> I think I see what you mean, but care to show an RFC patch ?
>>
>> --
> 
> Its not the controller driver, but he hardware limitation with older
> controller version. I have tried to see how I can do this better,
> however when spi_flash_read() is called  cannot handle it within my
> driver without returning from the function. I went over this with Mark
> previously and this current solution seemed reasonable. Any other
> solution outside of the generic driver would replicate a lot of code
> unnecessarily.

Hmmm, I kinda see the problem. I was thinking splitting the m25p80_read
function could be the solution and invoking the second part from the
driver if applicable, but this cannot work because the driver does not
know when it's interacting with SPI NOR and when with something else .

Can you tell me about the conditions under which the bcm controller
fails and should fall back to standard spi read ?

-- 
Best regards,
Marek Vasut