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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id s16sm1403323iow.47.2020.09.03.07.41.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Sep 2020 07:41:29 -0700 (PDT) Subject: Re: [PATCH] media: dvb-frontends/cxd2099: report errors To: Mauro Carvalho Chehab Cc: jasmin@anw.at, o.endriss@gmx.de, rjkm@metzlerbros.de, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200722134126.31191-1-trix@redhat.com> <20200903161328.62378992@coco.lan> From: Tom Rix Message-ID: Date: Thu, 3 Sep 2020 07:41:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200903161328.62378992@coco.lan> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 9/3/20 7:13 AM, Mauro Carvalho Chehab wrote: > Em Wed, 22 Jul 2020 06:41:26 -0700 > trix@redhat.com escreveu: > >> From: Tom Rix >> >> Clang static analysis reports this error >> >> drivers/media/dvb-frontends/cxd2099.c:420:2: warning: Undefined >> or garbage value returned to caller >> return val; >> ^~~~~~~~~~ >> >> In read_cam_control, the call to read_io can fail. >> When it fails val is not set. >> >> The failure status should be returned to the caller, >> not the unset val. >> >> Similar problem with read_attribute_mem >> >> Fixes: 0f0b270f905b ("[media] ngene: CXD2099AR Common Interface driver") >> >> Signed-off-by: Tom Rix >> --- >> drivers/media/dvb-frontends/cxd2099.c | 14 ++++++++++---- >> 1 file changed, 10 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/media/dvb-frontends/cxd2099.c b/drivers/media/dvb-frontends/cxd2099.c >> index f88b5355493e..9dfaf18fc4b4 100644 >> --- a/drivers/media/dvb-frontends/cxd2099.c >> +++ b/drivers/media/dvb-frontends/cxd2099.c >> @@ -387,12 +387,15 @@ static int read_attribute_mem(struct dvb_ca_en50221 *ca, >> { >> struct cxd *ci = ca->data; >> u8 val; >> + int ret; >> >> mutex_lock(&ci->lock); >> set_mode(ci, 1); >> - read_pccard(ci, address, &val, 1); >> + ret = read_pccard(ci, address, &val, 1); >> + if (!ret) >> + ret = val; >> mutex_unlock(&ci->lock); >> - return val; >> + return ret; >> } >> >> static int write_attribute_mem(struct dvb_ca_en50221 *ca, int slot, >> @@ -412,12 +415,15 @@ static int read_cam_control(struct dvb_ca_en50221 *ca, >> { >> struct cxd *ci = ca->data; >> unsigned int val; >> + int ret; >> >> mutex_lock(&ci->lock); >> set_mode(ci, 0); >> - read_io(ci, address, &val); >> + ret = read_io(ci, address, &val); >> + if (!ret) >> + ret = val; >> mutex_unlock(&ci->lock); >> - return val; >> + return ret; >> } >> >> static int write_cam_control(struct dvb_ca_en50221 *ca, int slot, > Hmm... Had you test this one on a real hardware? It is not > uncommon to have some DVB devices that would fail reading > when the firmware is on cold state. > > Without testing a patch like that at a real hardware, there's > no way to know if this is intentional or if the original > developer forgot to add a check for the error. No, I do not have hw.  I understand your concerns, it is ok if you want to drop this patch, else i'll beef up the warnings. Tom > > So, at most, it could print some warning message for > non-zero return codes. > > > Thanks, > Mauro >