netdev - Re: [PATCH v3 01/11] can: Add LIN bus as CAN abstraction

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Date: Wed, 8 May 2024 16:08:15 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Christoph Fritz <christoph.fritz@...dev.de>
cc: Oliver Hartkopp <socketcan@...tkopp.net>, 
    Marc Kleine-Budde <mkl@...gutronix.de>, Jiri Slaby <jirislaby@...nel.org>, 
    Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
    "David S . Miller" <davem@...emloft.net>, 
    Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
    Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, 
    Krzysztof Kozlowski <krzk+dt@...nel.org>, 
    Conor Dooley <conor+dt@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
    Benjamin Tissoires <bentiss@...nel.org>, 
    Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    Sebastian Reichel <sre@...nel.org>, 
    Linus Walleij <linus.walleij@...aro.org>, 
    Andreas Lauser <andreas.lauser@...cedes-benz.com>, 
    Jonathan Corbet <corbet@....net>, Pavel Pisa <pisa@....felk.cvut.cz>, 
    linux-can@...r.kernel.org, Netdev <netdev@...r.kernel.org>, 
    devicetree@...r.kernel.org, linux-input@...r.kernel.org, 
    linux-serial <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3 01/11] can: Add LIN bus as CAN abstraction

On Wed, 8 May 2024, Christoph Fritz wrote:

> On Mon, 2024-05-06 at 19:24 +0300, Ilpo Järvinen wrote:
> > On Thu, 2 May 2024, Christoph Fritz wrote:
> > 
> > > This patch adds a LIN (local interconnect network) bus abstraction on
> > > top of CAN.  It is a glue driver adapting CAN on one side while offering
> > > LIN abstraction on the other side. So that upcoming LIN device drivers
> > > can make use of it.

> > > +static int lin_create_sysfs_id_files(struct net_device *ndev)
> > > +{
> > > +	struct lin_device *ldev = netdev_priv(ndev);
> > > +	struct kobj_attribute *attr;
> > > +	int ret;
> > > +
> > > +	for (int id = 0; id < LIN_NUM_IDS; id++) {
> > > +		ldev->sysfs_entries[id].ldev = ldev;
> > > +		attr = &ldev->sysfs_entries[id].attr;
> > > +		attr->attr.name = kasprintf(GFP_KERNEL, "%02x", id);
> > > +		if (!attr->attr.name)
> > > +			return -ENOMEM;
> > > +		attr->attr.mode = 0644;
> > > +		attr->show = lin_identifier_show;
> > > +		attr->store = lin_identifier_store;
> > > +
> > > +		sysfs_attr_init(&attr->attr);
> > > +		ret = sysfs_create_file(ldev->lin_ids_kobj, &attr->attr);
> > > +		if (ret) {
> > > +			kfree(attr->attr.name);
> > > +			return -ENOMEM;
> > > +		}
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > 
> > Can you use .dev_groups instead ?
> 
> I'm not sure where to attach this in this glue code here. Should I do a
> class_register() and add the .dev_groups there?

I guess struct class would be correct direction but I'm not sure if it's 
viable in this case. It would avoid the need for custom sysfs setup code
if it's workable.

> > FWIW, this function doesn't do rollback when error occurs.
> 
> OK, this issue can be fixed in revision v4.
> 
> ...

> > > diff --git a/include/uapi/linux/can/netlink.h b/include/uapi/linux/can/netlink.h
> > > index 02ec32d694742..51b0e2a7624e4 100644
> > > --- a/include/uapi/linux/can/netlink.h
> > > +++ b/include/uapi/linux/can/netlink.h
> > > @@ -103,6 +103,7 @@ struct can_ctrlmode {
> > >  #define CAN_CTRLMODE_CC_LEN8_DLC	0x100	/* Classic CAN DLC option */
> > >  #define CAN_CTRLMODE_TDC_AUTO		0x200	/* CAN transiver automatically calculates TDCV */
> > >  #define CAN_CTRLMODE_TDC_MANUAL		0x400	/* TDCV is manually set up by user */
> > 
> > BIT(x) is these days available also for uapi I think.
> > 
> > > +#define CAN_CTRLMODE_LIN		0x800	/* LIN bus mode */
> 
> So, should I use just BIT(11) for the new define, or should I also
> refactor the whole list while at it?

Either is fine for me.

-- 
 i.