Re: [PATCH v2 3/5] Add initial support for alienware graphics amplifier.

[Mario Limonciello]

On 02/02/2016 11:24 AM, Darren Hart wrote:
> On Mon, Feb 01, 2016 at 08:28:49PM -0600, Mario Limonciello wrote:
>> The alienware graphics amplifier is a device that provides external
>> access to a full PCIe slot, USB hub, and additional control zone.
>>
>> This patch enables support for reading status whether the cable is
>> plugged in as well as for setting the colors in the new zone.
> Is this "new zone" related to the alienware graphics amplifier?

Yes it is.  The interface allows for changing it even if the amplifier
isn't plugged in. 
When it gets plugged in, that zone would be set to the color picked
previously.

>
>> Signed-off-by: Mario Limonciello <mario_limonciello@xxxxxxxx>
>> ---
>>  drivers/platform/x86/alienware-wmi.c | 110 +++++++++++++++++++++++++++++------
>>  1 file changed, 91 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/platform/x86/alienware-wmi.c b/drivers/platform/x86/alienware-wmi.c
>> index 8e8ea4f..e6f6322 100644
>> --- a/drivers/platform/x86/alienware-wmi.c
>> +++ b/drivers/platform/x86/alienware-wmi.c
>> @@ -33,6 +33,7 @@
>>  #define WMAX_METHOD_BRIGHTNESS		0x3
>>  #define WMAX_METHOD_ZONE_CONTROL	0x4
>>  #define WMAX_METHOD_HDMI_CABLE		0x5
>> +#define WMAX_METHOD_AMPLIFIER_CABLE	0x6
>>  
>>  MODULE_AUTHOR("Mario Limonciello <mario_limonciello@xxxxxxxx>");
>>  MODULE_DESCRIPTION("Alienware special feature control");
>> @@ -60,6 +61,7 @@ enum WMAX_CONTROL_STATES {
>>  struct quirk_entry {
>>  	u8 num_zones;
>>  	u8 hdmi_mux;
>> +	u8 amplifier;
>>  };
>>  
>>  static struct quirk_entry *quirks;
>> @@ -67,21 +69,25 @@ static struct quirk_entry *quirks;
>>  static struct quirk_entry quirk_unknown = {
>>  	.num_zones = 2,
>>  	.hdmi_mux = 0,
>> +	.amplifier = 0,
>>  };
>>  
>>  static struct quirk_entry quirk_x51_r1_r2 = {
>>  	.num_zones = 3,
>> -	.hdmi_mux = 0.
>> +	.hdmi_mux = 0,
>> +	.amplifier = 0,
>>  };
>>  
>>  static struct quirk_entry quirk_x51_r3 = {
>>  	.num_zones = 4,
>>  	.hdmi_mux = 0,
>> +	.amplifier = 1,
>>  };
>>  
>>  static struct quirk_entry quirk_asm100 = {
>>  	.num_zones = 2,
>>  	.hdmi_mux = 1,
>> +	.amplifier = 0,
>>  };
>>  
>>  static int __init dmi_matched(const struct dmi_system_id *dmi)
>> @@ -147,7 +153,7 @@ struct wmax_brightness_args {
>>  	u32 percentage;
>>  };
>>  
>> -struct hdmi_args {
>> +struct wmax_basic_args {
>>  	u8 arg;
>>  };
>>  
>> @@ -232,16 +238,16 @@ static int alienware_update_led(struct platform_zone *zone)
>>  	char *guid;
>>  	struct acpi_buffer input;
>>  	struct legacy_led_args legacy_args;
>> -	struct wmax_led_args wmax_args;
>> +	struct wmax_led_args wmax_basic_args;
>>  	if (interface == WMAX) {
>> -		wmax_args.led_mask = 1 << zone->location;
>> -		wmax_args.colors = zone->colors;
>> -		wmax_args.state = lighting_control_state;
>> +		wmax_basic_args.led_mask = 1 << zone->location;
>> +		wmax_basic_args.colors = zone->colors;
>> +		wmax_basic_args.state = lighting_control_state;
>>  		guid = WMAX_CONTROL_GUID;
>>  		method_id = WMAX_METHOD_ZONE_CONTROL;
>>  
>> -		input.length = (acpi_size) sizeof(wmax_args);
>> -		input.pointer = &wmax_args;
>> +		input.length = (acpi_size) sizeof(wmax_basic_args);
>> +		input.pointer = &wmax_basic_args;
>>  	} else {
>>  		legacy_args.colors = zone->colors;
>>  		legacy_args.brightness = global_brightness;
>> @@ -449,11 +455,7 @@ static void alienware_zone_exit(struct platform_device *dev)
>>  	kfree(zone_attrs);
>>  }
>>  
>> -/*
>> -	The HDMI mux sysfs node indicates the status of the HDMI input mux.
>> -	It can toggle between standard system GPU output and HDMI input.
>> -*/
>> -static acpi_status alienware_hdmi_command(struct hdmi_args *in_args,
>> +static acpi_status alienware_wmax_command(struct wmax_basic_args *in_args,
>>  					  u32 command, int *out_data)
>>  {
>>  	acpi_status status;
>> @@ -481,16 +483,20 @@ static acpi_status alienware_hdmi_command(struct hdmi_args *in_args,
>>  
>>  }
>>  
>> +/*
>> + *	The HDMI mux sysfs node indicates the status of the HDMI input mux.
>> + *	It can toggle between standard system GPU output and HDMI input.
>> +*/
> Nit, the last * should align with the preceding, same in comment blocks below.

OK, will fix in next submission.

>>  static ssize_t show_hdmi_cable(struct device *dev,
>>  			       struct device_attribute *attr, char *buf)
>>  {
>>  	acpi_status status;
>>  	u32 out_data;
>> -	struct hdmi_args in_args = {
>> +	struct wmax_basic_args in_args = {
>>  		.arg = 0,
>>  	};
>>  	status =
>> -	    alienware_hdmi_command(&in_args, WMAX_METHOD_HDMI_CABLE,
>> +	    alienware_wmax_command(&in_args, WMAX_METHOD_HDMI_CABLE,
>>  				   (u32 *) &out_data);
>>  	if (ACPI_SUCCESS(status)) {
>>  		if (out_data == 0)
>> @@ -509,11 +515,11 @@ static ssize_t show_hdmi_source(struct device *dev,
>>  {
>>  	acpi_status status;
>>  	u32 out_data;
>> -	struct hdmi_args in_args = {
>> +	struct wmax_basic_args in_args = {
>>  		.arg = 0,
>>  	};
>>  	status =
>> -	    alienware_hdmi_command(&in_args, WMAX_METHOD_HDMI_STATUS,
>> +	    alienware_wmax_command(&in_args, WMAX_METHOD_HDMI_STATUS,
>>  				   (u32 *) &out_data);
>>  
>>  	if (ACPI_SUCCESS(status)) {
>> @@ -533,7 +539,7 @@ static ssize_t toggle_hdmi_source(struct device *dev,
>>  				  const char *buf, size_t count)
>>  {
>>  	acpi_status status;
>> -	struct hdmi_args args;
>> +	struct wmax_basic_args args;
>>  	if (strcmp(buf, "gpu\n") == 0)
>>  		args.arg = 1;
>>  	else if (strcmp(buf, "input\n") == 0)
>> @@ -542,7 +548,7 @@ static ssize_t toggle_hdmi_source(struct device *dev,
>>  		args.arg = 3;
>>  	pr_debug("alienware-wmi: setting hdmi to %d : %s", args.arg, buf);
>>  
>> -	status = alienware_hdmi_command(&args, WMAX_METHOD_HDMI_SOURCE, NULL);
>> +	status = alienware_wmax_command(&args, WMAX_METHOD_HDMI_SOURCE, NULL);
>>  
>>  	if (ACPI_FAILURE(status))
>>  		pr_err("alienware-wmi: HDMI toggle failed: results: %u\n",
>> @@ -585,6 +591,65 @@ error_create_hdmi:
>>  	return ret;
> All of the above hdmi to wmax changes seem strange/out-of-place in the context
> of this patch. Are these a functionally independent change that could be done
> independently? If not, can you comment on why we're making this change? Sorry if
> it's obvious.

Before this platform was released we defined the interface of extended
commands to support only HDMI toggling on ASM100.  Later on after more
platforms were released (X51-R3 and others) the interface was extended
to support other commands that weren't envisioned originally.  Because
of this it makes more sense to call these "wmax" commands.

>>  }
>>  
>> +/* Alienware GFX amplifier support
>> + * - Currently supports reading cable status
>> + * - Leaving expansion room to possibly support dock/undock events later
>> +*/
>> +static ssize_t show_amplifier_status(struct device *dev,
>> +				     struct device_attribute *attr, char *buf)
>> +{
>> +	acpi_status status;
>> +	u32 out_data;
>> +	struct wmax_basic_args in_args = {
>> +		.arg = 0,
>> +	};
>> +	status =
>> +	    alienware_wmax_command(&in_args, WMAX_METHOD_AMPLIFIER_CABLE,
>> +				   (u32 *) &out_data);
>> +	if (ACPI_SUCCESS(status)) {
>> +		if (out_data == 0)
>> +			return scnprintf(buf, PAGE_SIZE,
>> +					 "[unconnected] connected unknown\n");
>> +		else if (out_data == 1)
>> +			return scnprintf(buf, PAGE_SIZE,
>> +					 "unconnected [connected] unknown\n");
>> +	}
>> +	pr_err("alienware-wmi: unknown amplifier cable status: %d\n", status);
>> +	return scnprintf(buf, PAGE_SIZE, "unconnected connected [unknown]\n");
>> +}
>> +
>> +static DEVICE_ATTR(status, S_IRUGO, show_amplifier_status, NULL);
>> +
>> +static struct attribute *amplifier_attrs[] = {
>> +	&dev_attr_status.attr,
>> +	NULL,
>> +};
>> +
>> +static struct attribute_group amplifier_attribute_group = {
>> +	.name = "amplifier",
>> +	.attrs = amplifier_attrs,
>> +};
>> +
>> +static void remove_amplifier(struct platform_device *dev)
>> +{
>> +	if (quirks->amplifier > 0)
>> +		sysfs_remove_group(&dev->dev.kobj, &amplifier_attribute_group);
>> +}
>> +
>> +static int create_amplifier(struct platform_device *dev)
>> +{
>> +	int ret;
>> +
>> +	ret = sysfs_create_group(&dev->dev.kobj, &amplifier_attribute_group);
>> +	if (ret)
>> +		goto error_create_amplifier;
>> +	return 0;
>> +
>> +error_create_amplifier:
>> +	remove_amplifier(dev);
>> +	return ret;
> The goto label isn't necessary here:
>
> if (ret)
> 	remove_amplifier(dev);
> return ret;
>
> This covers the error and success case and is 4 lines shorter.

OK, will fix in next submission.

>> +}
>> +
>>  static int __init alienware_wmi_init(void)
>>  {
>>  	int ret;
>> @@ -620,6 +685,12 @@ static int __init alienware_wmi_init(void)
>>  			goto fail_prep_hdmi;
>>  	}
>>  
>> +	if (quirks->amplifier > 0) {
>> +		ret = create_amplifier(platform_device);
>> +		if (ret)
>> +			goto fail_prep_amplifier;
> Do you feel the "right thing" to do here is to fail hard? Would it be possible
> to load the driver without amplifier support instead?
>
> I don't care which you choose, I just want to have the discussion. Sometimes
> we'll match a platform and fail on something like this and abort, which in turns
> removes functionality the user could otherwise benefit from.
>
> Your call.

Technically yes I think it would be possible to load it without
amplifier support, but I gave this some thought and really I want
everything powered by this interface to be all or nothing.  If parts of
it aren't present and userspace apps expect them (by the DMI data for
the platform) it will be another layer to debug what went wrong.  Given
how simple the initialization of create_amplifier is, if there is a
failure I'm expecting some other more interesting kernel or memory usage
problems need to be debugged anyhow :)

>
>> +	}
>> +
>>  	ret = alienware_zone_init(platform_device);
>>  	if (ret)
>>  		goto fail_prep_zones;
>> @@ -628,6 +699,7 @@ static int __init alienware_wmi_init(void)
>>  
>>  fail_prep_zones:
>>  	alienware_zone_exit(platform_device);
>> +fail_prep_amplifier:
>>  fail_prep_hdmi:
>>  	platform_device_del(platform_device);
>>  fail_platform_device2:
>> -- 
>> 1.9.1
>>
>>