On 12/1/2023 6:32 AM, Alexander Lobakin wrote:
> From: Jesse Brandeburg <jesse.brandeb...@intel.com>
>> --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
>> +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
>> @@ -505,7 +505,7 @@ static void idpf_rx_post_buf_refill(struct idpf_sw_queue
>> *refillq, u16 buf_id)
>>
>> /* store the buffer ID and the SW maintained GEN bit to the refillq */
>> refillq->ring[nta] =
>> - ((buf_id << IDPF_RX_BI_BUFID_S) & IDPF_RX_BI_BUFID_M) |
>> + FIELD_PREP(IDPF_RX_BI_BUFID_M, buf_id) |
>> (!!(test_bit(__IDPF_Q_GEN_CHK, refillq->flags)) <<
>> IDPF_RX_BI_GEN_S);
>
> Why isn't that one converted as well?
Because it's not a constant, and it's not checking a mask with "&", so
the automation ignored it. I *did* a test, and we could convert the
return value from test_bit (a bool) into the IDPF_RX_BI_GEN_M mask with
FIELD_PREP, since C-code allows the luxury of converting a bool to a
"1", even though it's a bit type ugly in this age of strict typing.
>
>>
>> @@ -1825,14 +1825,14 @@ static bool idpf_tx_clean_complq(struct idpf_queue
>> *complq, int budget,
>> u16 gen;
>>
>> /* if the descriptor isn't done, no work yet to do */
>> - gen = (le16_to_cpu(tx_desc->qid_comptype_gen) &
>> - IDPF_TXD_COMPLQ_GEN_M) >> IDPF_TXD_COMPLQ_GEN_S;
>> + gen = FIELD_GET(IDPF_TXD_COMPLQ_GEN_M,
>> + le16_to_cpu(tx_desc->qid_comptype_gen));
>
> The definition:
>
> #define IDPF_TXD_COMPLQ_GEN_M BIT_ULL(IDPF_TXD_COMPLQ_GEN_S)
>
> Please don't use FIELD_*() API for 1 bit.
Did you mean that gen is effectively used as a bool? I think that has
nothing to do with my change over to FIELD_GET, but I could see how
redesigning this code would be useful, but not as part of this
conversion series.
>
> gen = !!(le16_to_cpu(tx_desc->qid_comptype_gen) &
> IDPF_TXD_COMPLQ_GEN_M);
>
> is enough.
Generally I'd prefer that the kind of check above returned a bool with a
constant conversion of the mask (compile time) to an LE16 mask, and then
use that, which is why all of our other drivers do that instead.
>
> Moreover, you could use le*_{get,encode,replace}_bits() to get/set LE
> values right away without 2-step operation (from/to CPU + masks), but
> you didn't do that here (see below for an example).
Those aren't widely used yet in our drivers so I wasn't picking them up
yet. But thank you for pointing that out.
<snip>
> In general, I would say those two issues are very common in IDPF and
> also the whole your series converting the Intel drivers. The scripts
> won't check whether the mask has only 1 bit or whether the value gets
> converted from/to LE, so they won't help here.
I had been hoping to do some more followup work. it's possible that with
some tweaking the coccinelle script could learn how to detect non-pow2
constants, and therefore possibly one bit constants as well. Maybe
@Julia can help us refine the script and possibly get it into the
scripts/coccinelle directory to help other drivers as well.
> Could you maybe manually recheck all the places where bitfield masks are
> used at least in IDPF (better in ice, iavf, i40e, ..., as well) and
> posted a series that would address them? At the end, manual work is more
> valuable than automated conversions :p
I think a followup series would work better for this, do you agree?
Thanks,
Jesse
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