linux-kernel - Re: [PATCH v2] Serial: silabs si4455 serial driver

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Date:   Thu, 10 Dec 2020 19:46:25 +0000
From:   József Horváth <info@...istro.hu>
To:     'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>
Cc:     'Rob Herring' <robh+dt@...nel.org>,
        'Jiri Slaby' <jirislaby@...nel.org>,
        linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Serial: silabs si4455 serial driver

On Thu, Dec 10, 2020 at 08:03:22PM +0100, 'Greg Kroah-Hartman' wrote:
> On Thu, Dec 10, 2020 at 05:04:46PM +0000, József Horváth wrote:
> > This is a serial port driver for
> > Silicon Labs Si4455 Sub-GHz transciver.
> > 
> > Signed-off-by: József Horváth <info@...istro.hu>
> > ---
> >  .../bindings/serial/silabs,si4455.yaml        |   53 +
> >  MAINTAINERS                                   |    7 +
> >  drivers/tty/serial/Kconfig                    |    8 +
> >  drivers/tty/serial/Makefile                   |    1 +
> >  drivers/tty/serial/si4455.c                   | 1235 +++++++++++++++++
> >  drivers/tty/serial/si4455_api.h               |   56 +
> 
> First thing, a single .c file should not need a .h file.
> 
> But then I looked at the .h file and see:
> 
> > --- /dev/null
> > +++ b/drivers/tty/serial/si4455_api.h
> > @@ -0,0 +1,56 @@
> > +/* SPDX-License-Identifier: GPL-2.0
> > + *
> > + * Copyright (C) 2020 József Horváth <info@...istro.hu>
> > + *
> > + */
> > +#ifndef SI4455_API_H_
> > +#define SI4455_API_H_
> > +
> > +struct si4455_iocbuff {
> > +	uint32_t length;
> > +	uint8_t	data[4096];
> 
> If you do have an ioctl, use proper data types.  These are not the
> correct ones (hint, __u32 and __u8).
> 
> > +};
> > +
> > +#define BASE_TTYIOC_PRIVATE		0xA0
> > +/* Set EZConfig.
> > + * After this ioctl call, the driver restarts the si4455,
> > + * then apply the new configuration and patch.
> > + */
> > +#define SI4455_IOC_SEZC		_IOW('T', \
> > +				     BASE_TTYIOC_PRIVATE + 0x01, \
> > +				     struct si4455_iocbuff)
> 
> Why does a serial driver have private ioctls?  Please no, don't do that.

I checked the ioctl.h and serial_core.h, but I not found any similar definition, like BASE_VIDIOC_PRIVATE in videodev2.h.
In this case the name of macro BASE_TTYIOC_PRIVATE means the base value of special ioctl commands owned by this driver.

I can change it to BASE_TTYIOC or SI4455_IOC_BASE

> Implement the basic serial driver first, and then we can talk about
> "custom" configurations and the like, using the correct apis.

Without the SI4455_IOC_SEZC call, the driver can't configure the Si4455 and not working at all.
The cofiguration for interface is provided by user for application.
It contains the base frequency, channel spacing, modulation, and a lot of more stuff, and generated by Silicon Labs Wireless Development Suite.
The generated configuration is in a non public(compressed, encrypted...who knows) format, so without this the driver can't provide configuration parameters to Si4455.

> 
> thanks,
> 
> greg k-h

Üdvözlettel / Best regards:
József Horváth