Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964999AbdGTJwU (ORCPT ); Thu, 20 Jul 2017 05:52:20 -0400 Received: from mail-lf0-f47.google.com ([209.85.215.47]:38456 "EHLO mail-lf0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935653AbdGTJwP (ORCPT ); Thu, 20 Jul 2017 05:52:15 -0400 Subject: Re: [PATCH 1/4] can: dev: Add support for limiting configured bitrate To: Franklin S Cooper Jr , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, netdev@vger.kernel.org, linux-can@vger.kernel.org, wg@grandegger.com, mkl@pengutronix.de, robh+dt@kernel.org, quentin.schulz@free-electrons.com, dev.kurt@vandijck-laurijssen.be, andrew@lunn.ch References: <20170719233654.25908-1-fcooper@ti.com> <20170719233654.25908-2-fcooper@ti.com> From: Sergei Shtylyov Message-ID: Date: Thu, 20 Jul 2017 12:52:12 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170719233654.25908-2-fcooper@ti.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2098 Lines: 67 Hello! On 7/20/2017 2:36 AM, Franklin S Cooper Jr wrote: > Various CAN or CAN-FD IP may be able to run at a faster rate than > what the transceiver the CAN node is connected to. This can lead to > unexpected errors. However, CAN transceivers typically have fixed > limitations and provide no means to discover these limitations at > runtime. Therefore, add support for a fixed-transceiver node that > can be reused by other CAN peripheral drivers to determine for both > CAN and CAN-FD what the max bitrate that can be used. If the user > tries to configure CAN to pass these maximum bitrates it will throw > an error. > > Signed-off-by: Franklin S Cooper Jr > --- > drivers/net/can/dev.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/can/dev.h | 5 +++++ > 2 files changed, 53 insertions(+) > > diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c > index 365a8cc..fbab87d 100644 > --- a/drivers/net/can/dev.c > +++ b/drivers/net/can/dev.c [...] > @@ -814,6 +830,38 @@ int open_candev(struct net_device *dev) > } > EXPORT_SYMBOL_GPL(open_candev); > > +#ifdef CONFIG_OF > +void of_transceiver_is_fixed(struct net_device *dev) Strange name for a *void* function... Also, I think 'struct net_device *' variables are typically called 'ndev'. > +{ > + struct device_node *dn; > + struct can_priv *priv = netdev_priv(dev); > + u32 max_frequency; > + struct device_node *np; > + > + np = dev->dev.parent->of_node; > + > + /* New binding */ > + dn = of_get_child_by_name(np, "fixed-transceiver"); > + if (!dn) > + return; > + > + of_property_read_u32(dn, "max-arbitration-speed", &max_frequency); In case this function fails, 'max_frequency' will have no value -- you'd better initialize it... > + > + if (max_frequency > 0) > + priv->max_trans_arbitration_speed = max_frequency; > + else > + priv->max_trans_arbitration_speed = -1; > + > + of_property_read_u32(dn, "max-data-speed", &max_frequency); Again, when that function fails, the variable will keep the value from the previous call... [...] MBR, Sergei