linux-kernel - Re: [PATCH net 3/4] net: ipa: use the right accessor in ipa_endpoint_status

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Date:   Mon, 1 Feb 2021 16:02:04 -0800
From:   Amy Parker <enbyamy@...il.com>
To:     Alex Elder <elder@...aro.org>
Cc:     davem@...emloft.net, kuba@...nel.org, elder@...nel.org,
        evgreen@...omium.org, bjorn.andersson@...aro.org,
        cpratapa@...eaurora.org, subashab@...eaurora.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 3/4] net: ipa: use the right accessor in ipa_endpoint_status_skip()

On Mon, Feb 1, 2021 at 3:32 PM Alex Elder <elder@...aro.org> wrote:
>
> When extracting the destination endpoint ID from the status in
> ipa_endpoint_status_skip(), u32_get_bits() is used.  This happens to
> work, but it's wrong: the structure field is only 8 bits wide
> instead of 32.
>
> Fix this by using u8_get_bits() to get the destination endpoint ID.

Isn't

>
> Signed-off-by: Alex Elder <elder@...aro.org>
> ---
>  drivers/net/ipa/ipa_endpoint.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
> index 448d89da1e456..612afece303f3 100644
> --- a/drivers/net/ipa/ipa_endpoint.c
> +++ b/drivers/net/ipa/ipa_endpoint.c
> @@ -1164,8 +1164,8 @@ static bool ipa_endpoint_status_skip(struct ipa_endpoint *endpoint,
>                 return true;

A few lines above this, endpoint_id is initialized as u32. If we're
going for "correctness", endpoint_id should be a u8. But of course,
this would contrast with ipa_endpoint having it as a u32.


>         if (!status->pkt_len)
>                 return true;
> -       endpoint_id = u32_get_bits(status->endp_dst_idx,
> -                                  IPA_STATUS_DST_IDX_FMASK);
> +       endpoint_id = u8_get_bits(status->endp_dst_idx,
> +                                 IPA_STATUS_DST_IDX_FMASK);
>         if (endpoint_id != endpoint->endpoint_id)
>                 return true;
>
> --
> 2.27.0
>

As far as I see it, using u32_get_bits instead of u8_get_bits simply
eliminates confusion about the type of endpoint_id. Perhaps instead of
this patch, send a patch with a comment that while u32_get_bits is
used, the field is only 8 bits?

Best regards,
Amy Parker
(she/her/hers)