linux-kernel - Re: [PATCH v3 3/3] Input: Add TouchNetix axiom i2c touchscreen driver

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Message-ID: <ZT9uJMExvf7B0gtR@google.com>
Date:   Mon, 30 Oct 2023 08:49:40 +0000
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Kamel Bouhara <kamel.bouhara@...tlin.com>
Cc:     Marco Felsch <m.felsch@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Henrik Rydberg <rydberg@...math.org>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, mark.satterthwaite@...chnetix.com,
        bartp@...sheep.co.uk, hannah.rossiter@...chnetix.com,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        bsp-development.geo@...ca-geosystems.com
Subject: Re: [PATCH v3 3/3] Input: Add TouchNetix axiom i2c touchscreen driver

On Sun, Oct 22, 2023 at 09:35:29PM +0200, Kamel Bouhara wrote:
> On Fri, Oct 20, 2023 at 02:03:10PM +0200, Marco Felsch wrote:
> > > +
> > > +static int
> > > +axiom_i2c_write(struct i2c_client *client, u8 usage, u8 page, u8 *buf, u16 len)
> > > +{
> > > +	struct axiom_data *ts = i2c_get_clientdata(client);
> > > +	struct axiom_cmd_header cmd_header;
> > > +	struct i2c_msg msg[2];
> > > +	int ret;
> > > +
> > > +	cmd_header.target_address = cpu_to_le16(usage_to_target_address(ts, usage, page, 0));
> > > +	cmd_header.length = cpu_to_le16(len);
> > > +	cmd_header.read = 0;
> > > +
> > > +	msg[0].addr = client->addr;
> > > +	msg[0].flags = 0;
> > > +	msg[0].len = sizeof(cmd_header);
> > > +	msg[0].buf = (u8 *)&cmd_header;
> > > +
> > > +	msg[1].addr = client->addr;
> > > +	msg[1].flags = 0;
> > > +	msg[1].len = len;
> > > +	msg[1].buf = (char *)buf;
> >
> > Please check the "comms protocol app note", for write it is not allowed
> > to send a stop, so the whole data must be send in one i2c_msg.
> >
> 
> Well I only have the "Programmer's Guide", I'll have to check that as it
> really seems to works as it yet.

As far as I know we only send "stop" on the last message in a sequence
of messages in i2c_transfer() unless it is explicitly requested with
I2C_M_STOP flag.

...
> > > +
> > > +static void axiom_i2c_remove(struct i2c_client *client)
> > > +{
> > > +	struct axiom_data *ts = i2c_get_clientdata(client);
> > > +
> > > +	input_unregister_device(ts->input_dev);
> >
> > This can be part of devm_add_action_or_reset() and we could remove the
> > .remove() callback for this driver.
> >
> 
> Sure, thanks for the tips :)!

Actually input devices allocated with devm do not need to be explicitly
inregistered, so you do not need to bother with
devm_add_action_or_reset() and simply delete axiom_i2c_remove().

Thanks.

-- 
Dmitry