Re: [virtio-dev][PATCH V9 2/2] virtio-spi: add the device specification

[Harald Mommer <harald.mommer@opensynergy.com>]

Hello Haixu,
> There are such strange usage scenarios that frame size exceeds 32 
> bits, even 4096 bits. For these strange cases, It's impossible to use 
> only 32 bits bits_per_word_mask to enumerate all the conditions. Seems 
> that a similar situation exists in Linux spi driver also.
>
> Assume a case where the spi controller supports the frame size to be 
> any value from 16 to 64, 32 bits mask can only cover the 16 ~ 32 
> conditions.
>
> Even so, it's not a good idea to expand the bits_per_word_mask, 32 
> bits can cover most of the cases, except for some situations that are 
> not commonly used. Besides, it's hard to determine the bit width to 
> cover all the cases, and expanding will make the logic more 
> complicated. To summarize, I think the following statement is probably 
> proper:
>
> "\field{bits_per_word_mask} is a mask indicating which values of
> bits_per_word are supported. If bit n of \field{bits_per_word_mask} is 
> set, the bits_per_word with value (n+1) is supported. If 
> \field{bits_per_word_mask} is 0, there is no limitation for 
> bits_per_word."
>
> Do you think it is acceptable and appropriate?

Perfect.

Currently in the middle (almost done) of updating my software to draft V10.

Regards
Harald Mommer