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[73.185.129.58]) by smtp.googlemail.com with ESMTPSA id z10sm4631026ilm.19.2021.03.26.09.31.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Mar 2021 09:31:20 -0700 (PDT) Subject: Re: [greybus-dev] [PATCH] greybus: remove stray nul byte in apb_log_enable_read output To: Rasmus Villemoes , Johan Hovold , Alex Elder , Greg Kroah-Hartman Cc: greybus-dev@lists.linaro.org, linux-kernel@vger.kernel.org References: <20210326152254.733066-1-linux@rasmusvillemoes.dk> From: Alex Elder Message-ID: <3a04ad94-f8c3-4d2e-c6a2-d498ac3cbeb0@linaro.org> Date: Fri, 26 Mar 2021 11:31:20 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210326152254.733066-1-linux@rasmusvillemoes.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/26/21 10:22 AM, Rasmus Villemoes wrote: > Including a nul byte in the otherwise human-readable ascii output > from this debugfs file is probably not intended. Looking only at the comments above simple_read_from_buffer(), the last argument is the size of the buffer (tmp_buf in this case). So "3" is proper. But looking at callers, it seems that the trailing NUL is often excluded this way. I don't really have a problem with your patch, but could you explain why having the NUL byte included is an actual problem? A short statement about that would provide better context than just "probably not intended." Thanks. -Alex > > Signed-off-by: Rasmus Villemoes > --- > drivers/greybus/es2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/greybus/es2.c b/drivers/greybus/es2.c > index 48ad154df3a7..86a7fbc7fe13 100644 > --- a/drivers/greybus/es2.c > +++ b/drivers/greybus/es2.c > @@ -1171,7 +1171,7 @@ static ssize_t apb_log_enable_read(struct file *f, char __user *buf, > char tmp_buf[3]; > > sprintf(tmp_buf, "%d\n", enable); > - return simple_read_from_buffer(buf, count, ppos, tmp_buf, 3); > + return simple_read_from_buffer(buf, count, ppos, tmp_buf, 2); > } > > static ssize_t apb_log_enable_write(struct file *f, const char __user *buf, >