linux-kernel - Re: [PATCH 2/2] HID: logitech-hidpp: prefix the name with Logitech

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Message-ID: <20141210231739.GD4861@mail.corp.redhat.com>
Date:	Wed, 10 Dec 2014 18:17:40 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:	Peter Wu <peter@...ensteyn.nl>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Nestor Lopez Casado <nlopezcasad@...itech.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] HID: logitech-hidpp: prefix the name with Logitech

On Dec 11 2014 or thereabouts, Peter Wu wrote:
> On Wednesday 10 December 2014 17:21:10 Benjamin Tissoires wrote:
> > Current names are reported as "K750", "M705", and it can be misleading
> > for the users when they look at their input device list.
> > 
> > Prefixing the names with "Logitech " makes things better.
> 
> Doesn't this apply to all input devices? Like, every USB device can be
> queried for the manufacturer which could then by included by the input
> subsystem.

Yes and no. Yes, it's good to have the manufacturer name in the input
subsystem, and no, because usbhid already prepend the name with the
manufacturer.

> 
> What about duplicate names? Can this patch cause a conflict with devices
> having the same name?

I am not sure what you mean here. I am adding a prefix to the name, so I
do not see how a conflict can be possible. If there were a "M705" and a
"Logitech M705", with different wireless PID, that would be worrisome to
some extend.
But I am pretty sure this will not happen.

> 
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > ---
> > 
> > Hi Jiri,
> > 
> > I'd love to see this one in 3.19 (after a strong review, of course).
> > The idea came with the mouse DPI database that Peter is currently working on
> > (see http://who-t.blogspot.com.au/2014/12/building-a-dpi-database-for-mice.html).
> > 
> > I think, if you do not qualify the series for 3.19, we should drop it entirely.
> > 3.19 introduces the hidpp module and changes the labels. The DPI hwdb will check
> > on the label to match the actual mouse, so if this one does not get into 3.19,
> > we will end up in 3 entries for each Logitech device.
> > 
> > Cheers,
> > Benjamin
> > 
> > 
> >  drivers/hid/hid-logitech-hidpp.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> > index 3846305..8cf4352 100644
> > --- a/drivers/hid/hid-logitech-hidpp.c
> > +++ b/drivers/hid/hid-logitech-hidpp.c
> > @@ -282,6 +282,33 @@ static inline bool hidpp_report_is_connect_event(struct hidpp_report *report)
> >  		(report->rap.sub_id == 0x41);
> >  }
> >  
> > +/**
> > + * hidpp_prefix_name() prefixes the current given name with "Logitech ".
> > + */
> > +static void hidpp_prefix_name(char **name, int name_length)
> > +{
> > +#define PREFIX_SIZE 9 /* "Logitech " */
> > +
> > +	int new_length;
> > +	char *new_name;
> > +
> > +	if (name_length > PREFIX_SIZE &&
> > +	    strncmp(*name, "Logitech ", PREFIX_SIZE) == 0)
> 
> I think you meant || here, not &&.

No, I meant &&. The idea is to not add a prefix if the provided name
already contains the prefix. Read that as "if the size of the name may
contain the prefix and that the prefix is here, then we bail out".

> 
> > +		/* The prefix has is already in the name */
> > +		return;
> > +
> > +	new_length = name_length + PREFIX_SIZE;
> 
> Stylistic note, but 'PREFIX_SIZE + name_length' would match the order of
> the string that gets prepended.

Works for me.

I will send a v2 with your comments addressed.

Cheers,
Benjamin

> 
> Kind regards,
> Peter
> 
> > +	new_name = kzalloc(new_length, GFP_KERNEL);
> > +	if (!new_name)
> > +		return;
> > +
> > +	snprintf(new_name, new_length, "Logitech %s", *name);
> > +
> > +	kfree(*name);
> > +
> > +	*name = new_name;
> > +}
> > +
> >  /* -------------------------------------------------------------------------- */
> >  /* HIDP++ 1.0 commands                                                        */
> >  /* -------------------------------------------------------------------------- */
> > @@ -318,6 +345,10 @@ static char *hidpp_get_unifying_name(struct hidpp_device *hidpp_dev)
> >  		return NULL;
> >  
> >  	memcpy(name, &response.rap.params[2], len);
> > +
> > +	/* include the terminating '\0' */
> > +	hidpp_prefix_name(&name, len + 1);
> > +
> >  	return name;
> >  }
> >  
> > @@ -489,6 +520,9 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp)
> >  			feature_index, index, name + index,
> >  			__name_length - index);
> >  
> > +	/* include the terminating '\0' */
> > +	hidpp_prefix_name(&name, __name_length + 1);
> > +
> >  	return name;
> >  
> >  out_err:
> > 
> 
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