linux-kernel - Re: [PATCH v8 4/7] can: Add Nuvoton NCT6694 CANFD support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOoeyxUvoYsKpLMY6OU+Eo_4=Ka+au7e_awA4yVKswwtaDp6NQ@mail.gmail.com>
Date: Thu, 27 Mar 2025 13:30:58 +0800
From: Ming Yu <a0282524688@...il.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: tmyu0@...oton.com, lee@...nel.org, linus.walleij@...aro.org, brgl@...ev.pl, 
	andi.shyti@...nel.org, mailhol.vincent@...adoo.fr, andrew+netdev@...n.ch, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	wim@...ux-watchdog.org, linux@...ck-us.net, jdelvare@...e.com, 
	alexandre.belloni@...tlin.com, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org, 
	linux-can@...r.kernel.org, netdev@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-hwmon@...r.kernel.org, 
	linux-rtc@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v8 4/7] can: Add Nuvoton NCT6694 CANFD support

Marc Kleine-Budde <mkl@...gutronix.de> 於 2025年3月27日 週四 上午1:35寫道：
>
> > > > +static int nct6694_can_start(struct net_device *ndev)
> > > > +{
> > > > +     struct nct6694_can_priv *priv = netdev_priv(ndev);
> > > > +     const struct can_bittiming *d_bt = &priv->can.data_bittiming;
> > > > +     const struct can_bittiming *n_bt = &priv->can.bittiming;
> > > > +     struct nct6694_can_setting *setting __free(kfree) = NULL;
> > > > +     const struct nct6694_cmd_header cmd_hd = {
> > > > +             .mod = NCT6694_CAN_MOD,
> > > > +             .cmd = NCT6694_CAN_SETTING,
> > > > +             .sel = ndev->dev_port,
> > > > +             .len = cpu_to_le16(sizeof(*setting))
> > > > +     };
> > > > +     int ret;
> > > > +
> > > > +     setting = kzalloc(sizeof(*setting), GFP_KERNEL);
> > > > +     if (!setting)
> > > > +             return -ENOMEM;
> > > > +
> > > > +     setting->nbr = cpu_to_le32(n_bt->bitrate);
> > > > +     setting->dbr = cpu_to_le32(d_bt->bitrate);
> > >
> > > I just noticed one thing that needs clarification/documentation.
> > >
> > > You have nct6694_can_bittiming_nominal_const and
> > > nct6694_can_bittiming_data_const, but only pass the bit rates to your
> > > device.
> > >
> > > Do the bit timing const really reflect the HW limitations of your
> > > device?
> > >
> > > Are you sure your device uses the same algorithm as the kernel and
> > > calculates the same bit timing parameters as the kernel, so that the
> > > values given to the user space reflects the bit timing parameter chosen
> > > by your device?
> > >
> >
> > Originally, I only intended to provide NBR and DBR for user
> > configuration. In the next patch, I will add code to configure
> > NBTP(Nominal Bit Timing Prescaler) and DBTP(Data Bit Timing Prescaler)
> > based on the setting of nct6694_can_bittiming_nominal_const and
> > nct6694_can_bittiming_data_const.
>
> Sounds good, but this doesn't answer my questions:
>
> You have nct6694_can_bittiming_nominal_const and
> nct6694_can_bittiming_data_const, but only pass the bit rates and the
> prescaler to your device.
>

I understand.
The prescaler field is used to calculate sjw, brp, prop_seg,
phase_seg1 and phase_seg2. I will update the code in the next patch.


Thanks,
Ming