Re: [PATCH] Input: goodix-berlin - Add sysfs interface for reading and writing touch IC registers

[neil.armstrong@xxxxxxxxxx]

On 07/05/2024 04:13, Dmitry Torokhov wrote:
> On Mon, May 06, 2024 at 02:03:13PM +0200, Hans de Goede wrote:
> > Hi,
> >
> > On 5/6/24 1:47 PM, Charles Wang wrote:
> > > Export a sysfs interface that would allow reading and writing touchscreen
> > > IC registers. With this interface many things can be done in usersapce
> > > such as firmware updates. An example tool that utilizes this interface
> > > for performing firmware updates can be found at [1].
> >
> > I'm not sure if I'm a fan of adding an interface to export raw register
> > access for fwupdate.
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/touchscreen/goodix_fwupload.c
> >
> > Contains update support for older goodix touchscreens and it is not
> > that big. I think it might be better to just have an in kernel fwupdate
> > driver for this and have a sysfs file to which to write the new firmware.
> >
> > Adding Richard Hughes, fwupd maintainer to the Cc. Richard, do you have
> > any input on the suggested method for firmware updating ?
> >
> > If raw register access is seen as a good solution, then I think this
> > should use regmap + some generic helpers (to be written) to export
> > regmap r/w access to userspace.
>
> I think the less code we have in kernel the better, especially if in
> cases where firmware flashing is not essential for device to work (i.e.
> it the controller has a flash memory). That said IIRC Mark felt very
> strongly about allowing regmap writes from userspace... but maybe he
> softened the stance or we could have this functionality opt-in?

The update code is quite ugly, but we could probably limit the functionnality
and filtering the registers read/write to only the update registers.

Neil

> > > [1] https://github.com/goodix/fwupdate_for_berlin_linux
> >
> > Hmm, that tool seems to have some licensing issues there is an Apache License v2.0
> > LICENSE file, but the header of fwupdate.c claims it is confidential ...
> >
> > Regards,
> >
> > Hans
> >
> >
> > > Signed-off-by: Charles Wang <charles.goodix@xxxxxxxxx>
> > > ---
> > >   drivers/input/touchscreen/goodix_berlin.h     |  2 +
> > >   .../input/touchscreen/goodix_berlin_core.c    | 52 +++++++++++++++++++
> > >   drivers/input/touchscreen/goodix_berlin_i2c.c |  6 +++
> > >   drivers/input/touchscreen/goodix_berlin_spi.c |  6 +++
> > >   4 files changed, 66 insertions(+)
> > >
> > > diff --git a/drivers/input/touchscreen/goodix_berlin.h b/drivers/input/touchscreen/goodix_berlin.h
> > > index 1fd77eb69..1741f2d15 100644
> > > --- a/drivers/input/touchscreen/goodix_berlin.h
> > > +++ b/drivers/input/touchscreen/goodix_berlin.h
> > > @@ -19,6 +19,8 @@ struct regmap;
> > >   int goodix_berlin_probe(struct device *dev, int irq, const struct input_id *id,
> > >   			struct regmap *regmap);
> > >   
> > > +void goodix_berlin_remove(struct device *dev);
> > > +
> > >   extern const struct dev_pm_ops goodix_berlin_pm_ops;
> > >   
> > >   #endif
> > > diff --git a/drivers/input/touchscreen/goodix_berlin_core.c b/drivers/input/touchscreen/goodix_berlin_core.c
> > > index e7b41a926..e02160841 100644
> > > --- a/drivers/input/touchscreen/goodix_berlin_core.c
> > > +++ b/drivers/input/touchscreen/goodix_berlin_core.c
> > > @@ -672,6 +672,44 @@ static void goodix_berlin_power_off_act(void *data)
> > >   	goodix_berlin_power_off(cd);
> > >   }
> > >   
> > > +static ssize_t goodix_berlin_registers_read(struct file *filp, struct kobject *kobj,
> > > +	struct bin_attribute *bin_attr, char *buf, loff_t off, size_t count)
> > > +{
> > > +	struct goodix_berlin_core *cd;
> > > +	struct device *dev;
> > > +	int error;
> > > +
> > > +	dev = kobj_to_dev(kobj);
> > > +	cd = dev_get_drvdata(dev);
> > > +
> > > +	error = regmap_raw_read(cd->regmap, (unsigned int)off,
> > > +				buf, count);
> > > +
> > > +	return error ? error : count;
> > > +}
> > > +
> > > +static ssize_t goodix_berlin_registers_write(struct file *filp, struct kobject *kobj,
> > > +	struct bin_attribute *bin_attr, char *buf, loff_t off, size_t count)
> > > +{
> > > +	struct goodix_berlin_core *cd;
> > > +	struct device *dev;
> > > +	int error;
> > > +
> > > +	dev = kobj_to_dev(kobj);
> > > +	cd = dev_get_drvdata(dev);
> > > +
> > > +	error = regmap_raw_write(cd->regmap, (unsigned int)off,
> > > +				 buf, count);
> > > +
> > > +	return error ? error : count;
> > > +}
> > > +
> > > +static struct bin_attribute goodix_berlin_registers_attr = {
> > > +	.attr = {.name = "registers", .mode = 0600},
> > > +	.read = goodix_berlin_registers_read,
> > > +	.write = goodix_berlin_registers_write,
> > > +};
> > > +
> > >   int goodix_berlin_probe(struct device *dev, int irq, const struct input_id *id,
> > >   			struct regmap *regmap)
> > >   {
> > > @@ -743,6 +781,14 @@ int goodix_berlin_probe(struct device *dev, int irq, const struct input_id *id,
> > >   
> > >   	dev_set_drvdata(dev, cd);
> > >   
> > > +	error = sysfs_create_bin_file(&cd->dev->kobj,
> > > +				      &goodix_berlin_registers_attr);
>
> If we want to instantiate attributes from the driver please utilize
> dev_groups in respective driver structures to create and remove the
> attributes automatically.
>
> Thanks.