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In-Reply-To: <20200916165748.20927-1-alex.dewar90@gmail.com>
From:   Julian Calaby <julian.calaby@gmail.com>
Date:   Thu, 17 Sep 2020 10:45:33 +1000
Message-ID: <CAGRGNgWoFfCnK9FcWTf_f0b57JNEjsm6ZNQB5X_AMf8L3FyNcQ@mail.gmail.com>
Subject: Re: [PATCH v2] ath10k: sdio: remove redundant check in for loop
To:     Alex Dewar <alex.dewar90@gmail.com>
Cc:     Saeed Mahameed <saeedm@nvidia.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, ath10k@lists.infradead.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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Hi Alex,

On Thu, Sep 17, 2020 at 3:09 AM Alex Dewar <alex.dewar90@gmail.com> wrote:
>
> The for loop checks whether cur_section is NULL on every iteration, but
> we know it can never be NULL as there is another check towards the
> bottom of the loop body. Refactor to avoid this unnecessary check.
>
> Also, increment the variable i inline for clarity

Comments below.

> Addresses-Coverity: 1496984 ("Null pointer dereferences)
> Suggested-by: Saeed Mahameed <saeedm@nvidia.com>
> Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
> ---
> v2: refactor in the manner suggested by Saeed
>
>  drivers/net/wireless/ath/ath10k/sdio.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
> index 81ddaafb6721..486886c74e6a 100644
> --- a/drivers/net/wireless/ath/ath10k/sdio.c
> +++ b/drivers/net/wireless/ath/ath10k/sdio.c
> @@ -2307,8 +2307,8 @@ static int ath10k_sdio_dump_memory_section(struct ath10k *ar,
>         }
>
>         count = 0;
> -
> -       for (i = 0; cur_section; i++) {
> +       i = 0;
> +       for (; cur_section; cur_section = next_section) {

You can have multiple statements in each section of a for() if you need to, e.g.

for (i = 1; cur_section; cur_section = next_section, i++) {

which means that the increment of i isn't hidden deep in the function body.


That said, this function is a mess. Something (approximately) like
this might be more readable:

prev_end = memregion->start;
for (i = 0; i < mem_region->section_table.size; i++) {
    cur_section = &mem_region->section_table.sections[i];

    // fail if prev_end is greater than cur_section->start - message
from line 2329 and 2294
    // check section size - from line 2315

    skip_size = cur_section->start - prev_end;

    // check buffer size - from line 2339 - needs to account for the
skip size too.
    // fill in the skip size amount - from line 2358 and 2304
    // ath10k_sdio_read_mem - from line 2346

    prev_end = cur_section->end;
}

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/