Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
To:     Dan Murphy <dmurphy@ti.com>, wg@grandegger.com, davem@davemloft.net
Cc:     linux-can@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190319172651.10012-1-dmurphy@ti.com>
 <8b53474d-9dbf-4b81-defd-1587e022990b@pengutronix.de>
 <35d179a7-2682-111e-638b-903559f0974a@ti.com>
From:   Marc Kleine-Budde <mkl@pengutronix.de>
Openpgp: preference=signencrypt
Autocrypt: addr=mkl@pengutronix.de; prefer-encrypt=mutual; keydata=
 mQINBFFVq30BEACtnSvtXHoeHJxG6nRULcvlkW6RuNwHKmrqoksispp43X8+nwqIFYgb8UaX
 zu8T6kZP2wEIpM9RjEL3jdBjZNCsjSS6x1qzpc2+2ivjdiJsqeaagIgvy2JWy7vUa4/PyGfx
 QyUeXOxdj59DvLwAx8I6hOgeHx2X/ntKAMUxwawYfPZpP3gwTNKc27dJWSomOLgp+gbmOmgc
 6U5KwhAxPTEb3CsT5RicsC+uQQFumdl5I6XS+pbeXZndXwnj5t84M+HEj7RN6bUfV2WZO/AB
 Xt5+qFkC/AVUcj/dcHvZwQJlGeZxoi4veCoOT2MYqfR0ax1MmN+LVRvKm29oSyD4Ts/97cbs
 XsZDRxnEG3z/7Winiv0ZanclA7v7CQwrzsbpCv+oj+zokGuKasofzKdpywkjAfSE1zTyF+8K
 nxBAmzwEqeQ3iKqBc3AcCseqSPX53mPqmwvNVS2GqBpnOfY7Mxr1AEmxdEcRYbhG6Xdn+ACq
 Dq0Db3A++3PhMSaOu125uIAIwMXRJIzCXYSqXo8NIeo9tobk0C/9w3fUfMTrBDtSviLHqlp8
 eQEP8+TDSmRP/CwmFHv36jd+XGmBHzW5I7qw0OORRwNFYBeEuiOIgxAfjjbLGHh9SRwEqXAL
 kw+WVTwh0MN1k7I9/CDVlGvc3yIKS0sA+wudYiselXzgLuP5cQARAQABtCZNYXJjIEtsZWlu
 ZS1CdWRkZSA8bWtsQHBlbmd1dHJvbml4LmRlPokCVAQTAQoAPgIbAwIeAQIXgAULCQgHAwUV
 CgkICwUWAgMBABYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJcUsSbBQkM366zAAoJECte4hHF
 iupUgkAP/2RdxKPZ3GMqag33jKwKAbn/fRqAFWqUH9TCsRH3h6+/uEPnZdzhkL4a9p/6OeJn
 Z6NXqgsyRAOTZsSFcwlfxLNHVxBWm8pMwrBecdt4lzrjSt/3ws2GqxPsmza1Gs61lEdYvLST
 Ix2vPbB4FAfE0kizKAjRZzlwOyuHOr2ilujDsKTpFtd8lV1nBNNn6HBIBR5ShvJnwyUdzuby
 tOsSt7qJEvF1x3y49bHCy3uy+MmYuoEyG6zo9udUzhVsKe3hHYC2kfB16ZOBjFC3lH2U5An+
 yQYIIPZrSWXUeKjeMaKGvbg6W9Oi4XEtrwpzUGhbewxCZZCIrzAH2hz0dUhacxB201Y/faY6
 BdTS75SPs+zjTYo8yE9Y9eG7x/lB60nQjJiZVNvZ88QDfVuLl/heuIq+fyNajBbqbtBT5CWf
 mOP4Dh4xjm3Vwlz8imWW/drEVJZJrPYqv0HdPbY8jVMpqoe5jDloyVn3prfLdXSbKPexlJaW
 5tnPd4lj8rqOFShRnLFCibpeHWIumqrIqIkiRA9kFW3XMgtU6JkIrQzhJb6Tc6mZg2wuYW0d
 Wo2qvdziMgPkMFiWJpsxM9xPk9BBVwR+uojNq5LzdCsXQ2seG0dhaOTaaIDWVS8U/V8Nqjrl
 6bGG2quo5YzJuXKjtKjZ4R6k762pHJ3tnzI/jnlc1sXzuQENBFxSzJYBCAC58uHRFEjVVE3J
 31eyEQT6H1zSFCccTMPO/ewwAnotQWo98Bc67ecmprcnjRjSUKTbyY/eFxS21JnC4ZB0pJKx
 MNwK6zq71wLmpseXOgjufuG3kvCgwHLGf/nkBHXmSINHvW00eFK/kJBakwHEbddq8Dr4ewmr
 G7yr8d6A3CSn/qhOYWhIxNORK3SVo4Io7ExNX/ljbisGsgRzsWvY1JlN4sabSNEr7a8YaqTd
 2CfFe/5fPcQRGsfhAbH2pVGigr7JddONJPXGE7XzOrx5KTwEv19H6xNe+D/W3FwjZdO4TKIo
 vcZveSDrFWOi4o2Te4O5OB/2zZbNWPEON8MaXi9zABEBAAGJA3IEGAEKACYWIQTBQAugs5ie
 b7x9W1wrXuIRxYrqVAUCXFLMlgIbAgUJAeKNmgFACRArXuIRxYrqVMB0IAQZAQoAHRYhBJrx
 JF84Dn3PPNRrhVrGIaOR5J0gBQJcUsyWAAoJEFrGIaOR5J0grw4H/itil/yryJCvzi6iuZHS
 suSHHOiEf+UQHib1MLP96LM7FmDabjVSmJDpH4TsMu17A0HTG+bPMAdeia0+q9FWSvSHYW8D
 wNhfkb8zojpa37qBpVpiNy7r6BKGSRSoFOv6m/iIoRJuJ041AEKao6djj/FdQF8OV1EtWKRO
 +nE2bNuDCcwHkhHP+FHExdzhKSmnIsMjGpGwIQKN6DxlJ7fN4W7UZFIQdSO21ei+akinBo4K
 O0uNCnVmePU1UzrwXKG2sS2f97A+sZE89vkc59NtfPHhofI3JkmYexIF6uqLA3PumTqLQ2Lu
 bywPAC3YNphlhmBrG589p+sdtwDQlpoH9O7NeBAAg/lyGOUUIONrheii/l/zR0xxr2TDE6tq
 6HZWdtjWoqcaky6MSyJQIeJ20AjzdV/PxMkd8zOijRVTnlK44bcfidqFM6yuT1bvXAO6NOPy
 pvBRnfP66L/xECnZe7s07rXpNFy72XGNZwhj89xfpK4a9E8HQcOD0mNtCJaz7TTugqBOsQx2
 45VPHosmhdtBQ6/gjlf2WY9FXb5RyceeSuK4lVrz9uZB+fUHBge/giOSsrqFo/9fWAZsE67k
 6Mkdbpc7ZQwxelcpP/giB9N+XAfBsffQ8q6kIyuFV4ILsIECCIA4nt1rYmzphv6t5J6PmlTq
 TzW9jNzbYANoOFAGnjzNRyc9i8UiLvjhTzaKPBOkQfhStEJaZrdSWuR/7Tt2wZBBoNTsgNAw
 A+cEu+SWCvdX7vNpsCHMiHtcEmVt5R0Tex1Ky87EfXdnGR2mDi6Iyxi3MQcHez3C61Ga3Baf
 P8UtXR6zrrrlX22xXtpNJf4I4Z6RaLpB/avIXTFXPbJ8CUUbVD2R2mZ/jyzaTzgiABDZspbS
 gw17QQUrKqUog0nHXuaGGA1uvreHTnyBWx5P8FP7rhtvYKhw6XdJ06ns+2SFcQv0Bv6PcSDK
 aRXmnW+OsDthn84x1YkfGIRJEPvvmiOKQsFEiB4OUtTX2pheYmZcZc81KFfJMmE8Z9+LT6Ry
 uSS5AQ0EXFLNDgEIAL14qAzTMCE1PwRrYJRI/RSQGAGF3HLdYvjbQd9Ozzg02K3mNCF2Phb1
 cjsbMk/V6WMxYoZCEtCh4X2GjQG2GDDW4KC9HOa8cTmr9Vcno+f+pUle09TMzWDgtnH92WKx
 d0FIQev1zDbxU7lk1dIqyOjjpyhmR8Put6vgunvuIjGJ/GapHL/O0yjVlpumtmow6eME2muc
 TeJjpapPWBGcy/8VU4LM8xMeMWv8DtQML5ogyJxZ0Smt+AntIzcF9miV2SeYXA3OFiojQstF
 vScN7owL1XiQ3UjJotCp6pUcSVgVv0SgJXbDo5Nv87M2itn68VPfTu2uBBxRYqXQovsR++kA
 EQEAAYkCPAQYAQoAJhYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJcUs0OAhsMBQkB4o0iAAoJ
 ECte4hHFiupUbioQAJ40bEJmMOF28vFcGvQrpI+lfHJGk9zSrh4F4SlJyOVWV1yWyUAINr8w
 v1aamg2nAppZ16z4nAnGU/47tWZ4P8blLVG8x4SWzz3D7MCy1FsQBTrWGLqWldPhkBAGp2VH
 xDOK4rLhuQWx3H5zd3kPXaIgvHI3EliWaQN+u2xmTQSJN75I/V47QsaPvkm4TVe3JlB7l1Fg
 OmSvYx31YC+3slh89ayjPWt8hFaTLnB9NaW9bLhs3E2ESF9Dei0FRXIt3qnFV/hnETsx3X4h
 KEnXxhSRDVeURP7V6P/z3+WIfddVKZk5ZLHi39fJpxvsg9YLSfStMJ/cJfiPXk1vKdoa+FjN
 7nGAZyF6NHTNhsI7aHnvZMDavmAD3lK6CY+UBGtGQA3QhrUc2cedp1V53lXwor/D/D3Wo9wY
 iSXKOl4fFCh2Peo7qYmFUaDdyiCxvFm+YcIeMZ8wO5udzkjDtP4lWKAn4tUcdcwMOT5d0I3q
 WATP4wFI8QktNBqF3VY47HFwF9PtNuOZIqeAquKezywUc5KqKdqEWCPx9pfLxBAh3GW2Zfjp
 lP6A5upKs2ktDZOC2HZXP4IJ1GTk8hnfS4ade8s9FNcwu9m3JlxcGKLPq5DnIbPVQI1UUR4F
 QyAqTtIdSpeFYbvH8D7pO4lxLSz2ZyBMk+aKKs6GL5MqEci8OcFW
Subject: Re: [PATCH v11 1/5] can: m_can: Create a m_can platform framework
Message-ID: <b6d6daab-ff49-76d1-e363-6179100be560@pengutronix.de>
Date:   Thu, 9 May 2019 08:38:29 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <35d179a7-2682-111e-638b-903559f0974a@ti.com>
Content-Type: multipart/signed; micalg=pgp-sha512;
 protocol="application/pgp-signature";
 boundary="a3xXgYU38s46hzqdXcmCpGMtxhdaaPBt4"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
--a3xXgYU38s46hzqdXcmCpGMtxhdaaPBt4
Content-Type: multipart/mixed; boundary="VQj2Tbcz15jDp4XUoPDDM0DRxRoZdHHvZ";
 protected-headers="v1"
From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Dan Murphy <dmurphy@ti.com>, wg@grandegger.com, davem@davemloft.net
Cc: linux-can@vger.kernel.org, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org
Message-ID: <b6d6daab-ff49-76d1-e363-6179100be560@pengutronix.de>
Subject: Re: [PATCH v11 1/5] can: m_can: Create a m_can platform framework
References: <20190319172651.10012-1-dmurphy@ti.com>
 <8b53474d-9dbf-4b81-defd-1587e022990b@pengutronix.de>
 <35d179a7-2682-111e-638b-903559f0974a@ti.com>
In-Reply-To: <35d179a7-2682-111e-638b-903559f0974a@ti.com>

--VQj2Tbcz15jDp4XUoPDDM0DRxRoZdHHvZ
Content-Type: text/plain; charset=utf-8
Content-Language: de-DE
Content-Transfer-Encoding: quoted-printable

On 5/8/19 9:54 PM, Dan Murphy wrote:
>>> -/* m_can private data structure */
>>> -struct m_can_priv {
>>> -	struct can_priv can;	/* must be the first member */
>>> -	struct napi_struct napi;
>>> -	struct net_device *dev;
>>> -	struct device *device;
>>> -	struct clk *hclk;
>>> -	struct clk *cclk;
>>> -	void __iomem *base;
>>> -	u32 irqstatus;
>>> -	int version;
>>> -
>>> -	/* message ram configuration */
>>> -	void __iomem *mram_base;
>>> -	struct mram_cfg mcfg[MRAM_CFG_NUM];
>>> -};
>>> +static u32 m_can_read(struct m_can_priv *priv, enum m_can_reg reg)
>>> +{
>>> +	if (priv->ops->read_reg)
>>> +		return priv->ops->read_reg(priv, reg);
>>> +	else
>>> +		return -EINVAL;
>>> +}
>>
>> How do you plan to check the return value here?
>> What's the difference between a register value of 0xffffffe9 and
>> returning -EINVAL?
>=20
> Good point.  I could just inline this and return whatever is sent
> from the callback and as you said allow a backtrace to happen if
> read_reg is invalid.

ACK.
A minimal function will look like this:

static inline u32 m_can_read(struct m_can_priv *priv, enum m_can_reg reg)=

{
	return priv->ops->read_reg(priv, reg);
}

And of ops or read_reg is NULL, the kernel will access a NULL pointer
that would then generate a backtrace.

>>> -static inline u32 m_can_read(const struct m_can_priv *priv, enum m_c=
an_reg reg)
>>> +static int m_can_write(struct m_can_priv *priv, enum m_can_reg reg, =
u32 val)
>>>  {
>>> -	return readl(priv->base + reg);
>>> +	if (priv->ops->write_reg)
>>> +		return priv->ops->write_reg(priv, reg, val);
>>> +	else
>>> +		return -EINVAL;
>>>  }
>>
>> I don't see anyone checking the return value. Better just dereference
>> the pointer and the kernel will produce a nice backtrace.
>>
>> Same should be done for all read and write variants.
>>
>=20
> I will need to go through this and see if there is any caller checking =
the return.  But
> I think you are correct.  If thats true I will just change this to a vo=
id, inline the function
> and allow a backtrace if the callback is null

ok

regards,
Marc

--=20
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


--VQj2Tbcz15jDp4XUoPDDM0DRxRoZdHHvZ--

--a3xXgYU38s46hzqdXcmCpGMtxhdaaPBt4
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAEBCgAdFiEEmvEkXzgOfc881GuFWsYho5HknSAFAlzTyuUACgkQWsYho5Hk
nSBiEQgAomIXBCvMCBf188HH8++++IsfVDErPHlwIp+jyLFokfKE8bEUwxRR/U4R
oa7B9WgfoejxfrLsN0AnmhW4lIZPwCWjbSUcVnS/FxQfHBG3L37xwD/qr5hz7Wtx
CigXUeuKEQwH5phx7Ht+hDZNi1NCoAwuISekww7wTLlXGMRsJdmhrVFFaPk51S4o
LnQALH2bcuwJB0VAAjGdIg05X+VQcdISRYlqydol7uVdPbvvE7UuHvUZMzg59AzQ
wRT3s5nN5z+8d+41xtWYiFJgPQoUfFfIgrE+DppxaNxAbj9EqDVok1cylRmLiAcS
K6sbNLefiU1uhw9UusZgFjYuWu8PaA==
=7e44
-----END PGP SIGNATURE-----

--a3xXgYU38s46hzqdXcmCpGMtxhdaaPBt4--