linux-kernel - Re: [PATCH 2/2] hp-wmi: Fix detection for dock and tablet mode

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Date:   Thu, 13 Apr 2017 11:21:50 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Carlo Caione <carlo@...one.org>
Cc:     andy@...radead.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...lessm.com,
        Carlo Caione <carlo@...lessm.com>
Subject: Re: [PATCH 2/2] hp-wmi: Fix detection for dock and tablet mode

On Sun, Apr 09, 2017 at 03:56:08PM +0200, Carlo Caione wrote:
> From: Carlo Caione <carlo@...lessm.com>
> 
> The current driver code is not checking for the error values returned by
> 'hp_wmi_dock_state()' and 'hp_wmi_tablet_state()' before passing the
> returned values down to 'input_report_switch()'. This error code is
> being translated to '1' in the input subsystem, reporting the wrong
> status.
> 
> The biggest problem caused by this issue is that several laptops are
> wrongly reported by the driver as docked, preventing them to be put to
> sleep using the LID (and in most cases they are not even dockable).
> 
> With this patch we create the report switches only if we are able to
> read the dock and tablet mode status correctly from ACPI.
> 
> Signed-off-by: Carlo Caione <carlo@...lessm.com>
> ---
>  drivers/platform/x86/hp-wmi.c | 40 +++++++++++++++++++++++++++-------------
>  1 file changed, 27 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/platform/x86/hp-wmi.c b/drivers/platform/x86/hp-wmi.c
> index 13ba65c..2b721fd 100644
> --- a/drivers/platform/x86/hp-wmi.c
> +++ b/drivers/platform/x86/hp-wmi.c
> @@ -572,10 +572,12 @@ static void hp_wmi_notify(u32 value, void *context)
>  
>  	switch (event_id) {
>  	case HPWMI_DOCK_EVENT:
> -		input_report_switch(hp_wmi_input_dev, SW_DOCK,
> -				    hp_wmi_dock_state());
> -		input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE,
> -				    hp_wmi_tablet_state());
> +		if (test_bit(SW_DOCK, hp_wmi_input_dev->swbit))
> +			input_report_switch(hp_wmi_input_dev, SW_DOCK,
> +					    hp_wmi_dock_state());
> +		if (test_bit(SW_TABLET_MODE, hp_wmi_input_dev->swbit))
> +			input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE,
> +					    hp_wmi_tablet_state());
>  		input_sync(hp_wmi_input_dev);
>  		break;
>  	case HPWMI_PARK_HDD:
> @@ -644,6 +646,7 @@ static int __init hp_wmi_input_setup(void)
>  {
>  	acpi_status status;
>  	int err;
> +	int val;
>  
>  	hp_wmi_input_dev = input_allocate_device();
>  	if (!hp_wmi_input_dev)
> @@ -654,17 +657,26 @@ static int __init hp_wmi_input_setup(void)
>  	hp_wmi_input_dev->id.bustype = BUS_HOST;
>  
>  	__set_bit(EV_SW, hp_wmi_input_dev->evbit);
> -	__set_bit(SW_DOCK, hp_wmi_input_dev->swbit);
> -	__set_bit(SW_TABLET_MODE, hp_wmi_input_dev->swbit);
> +
> +	/* Dock */
> +	val = hp_wmi_dock_state();
> +	if (!(val < 0)) {
> +		__set_bit(SW_DOCK, hp_wmi_input_dev->swbit);
> +		input_report_switch(hp_wmi_input_dev, SW_DOCK, val);
> +	}

In general, these are fine and can go in. I did want to get your opinion on one
thought though.

This adds some complexity to deal with what appears to be an unknown failure
mode (the query fails, we don't know why, so we don't set the bit on the input
dev for that feature). Since we don't know why it fails, can we be confident it
will always fail? Could it succeed at init here, but then fail later and leave
us in the same situation we are in now?

If so, have you considered just returning 0 on error and using a WARN_ONCE print
statement to report the error? This would simplify a lot of this logic that
you're adding in here to handle something we could just report and ignore.

That being said, your version avoids the input_report_switch() in the event of a
failure at init. In practice, I don't know if this is worth the added
complexity.

Your thoughts?

> +
> +	/* Tablet mode */
> +	val = hp_wmi_tablet_state();
> +	if (!(val < 0)) {
> +		__set_bit(SW_TABLET_MODE, hp_wmi_input_dev->swbit);
> +		input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE, val);
> +	}
>  
>  	err = sparse_keymap_setup(hp_wmi_input_dev, hp_wmi_keymap, NULL);
>  	if (err)
>  		goto err_free_dev;
>  
>  	/* Set initial hardware state */
> -	input_report_switch(hp_wmi_input_dev, SW_DOCK, hp_wmi_dock_state());
> -	input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE,
> -			    hp_wmi_tablet_state());
>  	input_sync(hp_wmi_input_dev);
>  
>  	if (!hp_wmi_bios_2009_later() && hp_wmi_bios_2008_later())
> @@ -950,10 +962,12 @@ static int hp_wmi_resume_handler(struct device *device)
>  	 * changed.
>  	 */
>  	if (hp_wmi_input_dev) {
> -		input_report_switch(hp_wmi_input_dev, SW_DOCK,
> -				    hp_wmi_dock_state());
> -		input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE,
> -				    hp_wmi_tablet_state());
> +		if (test_bit(SW_DOCK, hp_wmi_input_dev->swbit))
> +			input_report_switch(hp_wmi_input_dev, SW_DOCK,
> +					    hp_wmi_dock_state());
> +		if (test_bit(SW_TABLET_MODE, hp_wmi_input_dev->swbit))
> +			input_report_switch(hp_wmi_input_dev, SW_TABLET_MODE,
> +					    hp_wmi_tablet_state());
>  		input_sync(hp_wmi_input_dev);
>  	}
>  
> -- 
> 2.9.3
> 
> 

-- 
Darren Hart
VMware Open Source Technology Center