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SubjectRe: [PATCH v4 2/2] tpm: add support for partial reads
On Sun, Nov 18, 2018 at 07:05:19PM -0800, Tadeusz Struk wrote:
> > When ret_size < 0? Shouldn't this be just "if (!ret_size)"?
>
> What we want to check here is if ret_size is positive, which is a valid
> value, or if it is negative or zero, which is an invalid value, so in
> this case (!ret_size) will not work.

Please explain a scenario where "!ret_size" would no work given that
both size and partial_data have always positive value?

> >> /* Holds the resul of the last successful call to tpm_transmit() */
> >> size_t transmit_result;
> >> + /* Holds the count how much of the response is still unread */
> >> + size_t partial_data;
> > I'm otherwise happy how this look like but why call it partial_data.
> > You cannot really tell from the name anything about its contents as
> > data is very abstract term.
>
> so I will rename these two to response_length and response_length_rem,
> how does this sound?

Yes, assuming that there would be a hard requirement to even have two
variables in the first place.

> > BTW, why you need the new variable anyway and not just decrease the
> > variable where the length is original stored?
>
> We need to have two variables, otherwise how do we tell if some part of
> response was consumed to allow sending a new command?

I don't understand. In order to maintain backwards compatibility you can
send a new command at any time.

> The transmit_result is used for that. If it is zero then one can transmit
> a new command even if the whole response is not consumed. The new variable
> tracks how much of the response is still to be read.

AFAIK you only need to track the latter, not both.

/Jarkko

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