[PATCH 0/2] Add support for USB accessories in the max77843 extcon driver

[PATCH 0/2] Add support for USB accessories in the max77843 extcon driver

[Andi Shyti]

Hi,

this patchset add handling of external USB accessories that are
connected to the extcon max77843 device.

The first patch is preparatory, that mainly aims to improve the
readability of the second patch. It makes some code refactoring
reducing the duplicated code, the result is exactly the same.

It has been tested on TM2 with mainline kernel 4.11-rc4.

Andi

Andi Shyti (2):
  extcon: max77843: improve the code and minimize duplicated lines
  extcon: max77843: support USB accessories as external USB hosts

 drivers/extcon/extcon-max77843.c | 50 ++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 30 deletions(-)

-- 
2.11.0

[PATCH 1/2] extcon: max77843: improve the code and minimize duplicated lines

[Andi Shyti]

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
---
 drivers/extcon/extcon-max77843.c | 33 ++++++++-------------------------
 1 file changed, 8 insertions(+), 25 deletions(-)

diff --git a/drivers/extcon/extcon-max77843.c b/drivers/extcon/extcon-max77843.c
index 6e722d552cf1..fcdabc4b4025 100644
--- a/drivers/extcon/extcon-max77843.c
+++ b/drivers/extcon/extcon-max77843.c
@@ -264,37 +264,20 @@ static int max77843_muic_get_cable_type(struct max77843_muic_info *info,
 		chg_type = info->status[MAX77843_MUIC_STATUS2] &
 				MAX77843_MUIC_STATUS2_CHGTYP_MASK;
 
-		/* Check GROUND accessory with charger cable */
-		if (adc == MAX77843_MUIC_ADC_GROUND) {
-			if (chg_type == MAX77843_MUIC_CHG_NONE) {
-				/*
-				 * The following state when charger cable is
-				 * disconnected but the GROUND accessory still
-				 * connected.
-				 */
-				*attached = false;
-				cable_type = info->prev_chg_type;
-				info->prev_chg_type = MAX77843_MUIC_CHG_NONE;
-			} else {
-
-				/*
-				 * The following state when charger cable is
-				 * connected on the GROUND accessory.
-				 */
-				*attached = true;
-				cable_type = MAX77843_MUIC_CHG_GND;
-				info->prev_chg_type = MAX77843_MUIC_CHG_GND;
-			}
-			break;
-		}
-
 		if (chg_type == MAX77843_MUIC_CHG_NONE) {
 			*attached = false;
 			cable_type = info->prev_chg_type;
 			info->prev_chg_type = MAX77843_MUIC_CHG_NONE;
 		} else {
 			*attached = true;
-			cable_type = info->prev_chg_type = chg_type;
+			switch (adc) {
+			case MAX77843_MUIC_ADC_GROUND:
+				info->prev_chg_type = MAX77843_MUIC_CHG_GND;
+				break;
+			default:
+				info->prev_chg_type = chg_type;
+			}
+			cable_type = info->prev_chg_type;
 		}
 		break;
 	case MAX77843_CABLE_GROUP_ADC_GND:
-- 
2.11.0

[PATCH 2/2] extcon: max77843: support USB accessories as external USB hosts

[Andi Shyti]

The ADC state defines the resistance that a USB device has in
order to distinguish between devices.

The external accessories (like the Gear VR) are defined as:

MAX77843_MUIC_ADC_RESERVED_ACC_1
MAX77843_MUIC_ADC_RESERVED_ACC_2
MAX77843_MUIC_ADC_RESERVED_ACC_3
MAX77843_MUIC_ADC_RESERVED_ACC_4
MAX77843_MUIC_ADC_RESERVED_ACC_5

and they should be set as such in the extcon driver.

Do not ignore interrupts generated by external accessories by
handling cables of the type from any of the above.

Do not handle any charging related action. This can be
misleading as also external devices might have some power and in
such cases the MUIC might consider them as power providers. In
this case check the value of the adc and if it corresponds to
one or the MAX77843_MUIC_ADC_RESERVED_ACC_*, return a no-action
value (MAX77843_MUIC_CHG_NONE).

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
---
 drivers/extcon/extcon-max77843.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/extcon/extcon-max77843.c b/drivers/extcon/extcon-max77843.c
index fcdabc4b4025..00795fe9ab60 100644
--- a/drivers/extcon/extcon-max77843.c
+++ b/drivers/extcon/extcon-max77843.c
@@ -271,6 +271,13 @@ static int max77843_muic_get_cable_type(struct max77843_muic_info *info,
 		} else {
 			*attached = true;
 			switch (adc) {
+			case MAX77843_MUIC_ADC_RESERVED_ACC_1:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_2:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_3:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_4:
+			case MAX77843_MUIC_ADC_RESERVED_ACC_5:
+				info->prev_chg_type = MAX77843_MUIC_CHG_NONE;
+				break;
 			case MAX77843_MUIC_ADC_GROUND:
 				info->prev_chg_type = MAX77843_MUIC_CHG_GND;
 				break;
@@ -403,6 +410,11 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
 
 	switch (cable_type) {
 	case MAX77843_MUIC_ADC_GROUND:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_1:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_2:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_3:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_4:
+	case MAX77843_MUIC_ADC_RESERVED_ACC_5:
 		ret = max77843_muic_adc_gnd_handler(info);
 		if (ret < 0)
 			return ret;
@@ -427,11 +439,6 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
 	case MAX77843_MUIC_ADC_REMOTE_S10_BUTTON:
 	case MAX77843_MUIC_ADC_REMOTE_S11_BUTTON:
 	case MAX77843_MUIC_ADC_REMOTE_S12_BUTTON:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_1:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_2:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_3:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_4:
-	case MAX77843_MUIC_ADC_RESERVED_ACC_5:
 	case MAX77843_MUIC_ADC_AUDIO_DEVICE_TYPE2:
 	case MAX77843_MUIC_ADC_PHONE_POWERED_DEV:
 	case MAX77843_MUIC_ADC_TTY_CONVERTER:
-- 
2.11.0

Re: [PATCH 2/2] extcon: max77843: support USB accessories as external USB hosts

[Krzysztof Kozlowski]

On Wed, Mar 29, 2017 at 2:54 PM, Andi Shyti <andi.shyti@samsung.com> wrote:
> The ADC state defines the resistance that a USB device has in
> order to distinguish between devices.
>
> The external accessories (like the Gear VR) are defined as:
>
> MAX77843_MUIC_ADC_RESERVED_ACC_1
> MAX77843_MUIC_ADC_RESERVED_ACC_2
> MAX77843_MUIC_ADC_RESERVED_ACC_3
> MAX77843_MUIC_ADC_RESERVED_ACC_4
> MAX77843_MUIC_ADC_RESERVED_ACC_5
>
> and they should be set as such in the extcon driver.
>
> Do not ignore interrupts generated by external accessories by
> handling cables of the type from any of the above.
>
> Do not handle any charging related action. This can be
> misleading as also external devices might have some power and in
> such cases the MUIC might consider them as power providers. In
> this case check the value of the adc and if it corresponds to
> one or the MAX77843_MUIC_ADC_RESERVED_ACC_*, return a no-action
> value (MAX77843_MUIC_CHG_NONE).
>
> Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
> ---
>  drivers/extcon/extcon-max77843.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/extcon/extcon-max77843.c b/drivers/extcon/extcon-max77843.c
> index fcdabc4b4025..00795fe9ab60 100644
> --- a/drivers/extcon/extcon-max77843.c
> +++ b/drivers/extcon/extcon-max77843.c
> @@ -271,6 +271,13 @@ static int max77843_muic_get_cable_type(struct max77843_muic_info *info,
>                 } else {
>                         *attached = true;
>                         switch (adc) {
> +                       case MAX77843_MUIC_ADC_RESERVED_ACC_1:
> +                       case MAX77843_MUIC_ADC_RESERVED_ACC_2:
> +                       case MAX77843_MUIC_ADC_RESERVED_ACC_3:
> +                       case MAX77843_MUIC_ADC_RESERVED_ACC_4:
> +                       case MAX77843_MUIC_ADC_RESERVED_ACC_5:

In commit msg you mentioned it but in code not. It looks weird to
handle a vague "reserved" type in a specific way. How about adding
some meaningful names instead of "reserved"? Or at least documenting,
that they match Gear VR. Really, imagine later one would be looking at
the code and trying to figure out why "reserved" means something

Best regards,
Krzysztof

> +                               info->prev_chg_type = MAX77843_MUIC_CHG_NONE;
> +                               break;
>                         case MAX77843_MUIC_ADC_GROUND:
>                                 info->prev_chg_type = MAX77843_MUIC_CHG_GND;
>                                 break;
> @@ -403,6 +410,11 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
>
>         switch (cable_type) {
>         case MAX77843_MUIC_ADC_GROUND:
> +       case MAX77843_MUIC_ADC_RESERVED_ACC_1:
> +       case MAX77843_MUIC_ADC_RESERVED_ACC_2:
> +       case MAX77843_MUIC_ADC_RESERVED_ACC_3:
> +       case MAX77843_MUIC_ADC_RESERVED_ACC_4:
> +       case MAX77843_MUIC_ADC_RESERVED_ACC_5:
>                 ret = max77843_muic_adc_gnd_handler(info);
>                 if (ret < 0)
>                         return ret;
> @@ -427,11 +439,6 @@ static int max77843_muic_adc_handler(struct max77843_muic_info *info)
>         case MAX77843_MUIC_ADC_REMOTE_S10_BUTTON:
>         case MAX77843_MUIC_ADC_REMOTE_S11_BUTTON:
>         case MAX77843_MUIC_ADC_REMOTE_S12_BUTTON:
> -       case MAX77843_MUIC_ADC_RESERVED_ACC_1:
> -       case MAX77843_MUIC_ADC_RESERVED_ACC_2:
> -       case MAX77843_MUIC_ADC_RESERVED_ACC_3:
> -       case MAX77843_MUIC_ADC_RESERVED_ACC_4:
> -       case MAX77843_MUIC_ADC_RESERVED_ACC_5:
>         case MAX77843_MUIC_ADC_AUDIO_DEVICE_TYPE2:
>         case MAX77843_MUIC_ADC_PHONE_POWERED_DEV:
>         case MAX77843_MUIC_ADC_TTY_CONVERTER:
> --
> 2.11.0
>

Re: [PATCH 2/2] extcon: max77843: support USB accessories as external USB hosts

[Andi Shyti]

Hi Krzysztof,

> > +                       case MAX77843_MUIC_ADC_RESERVED_ACC_1:
> > +                       case MAX77843_MUIC_ADC_RESERVED_ACC_2:
> > +                       case MAX77843_MUIC_ADC_RESERVED_ACC_3:
> > +                       case MAX77843_MUIC_ADC_RESERVED_ACC_4:
> > +                       case MAX77843_MUIC_ADC_RESERVED_ACC_5:
> 
> In commit msg you mentioned it but in code not. It looks weird to
> handle a vague "reserved" type in a specific way. How about adding
> some meaningful names instead of "reserved"? Or at least documenting,
> that they match Gear VR. Really, imagine later one would be looking at
> the code and trying to figure out why "reserved" means something

I know it's misleading, but that's the name from the datasheet,
that's why I tried to be more specific in the commit log.

In any case RESERVED_ACC stands for "reserved for external
accessory".

The Gear VR corresponds to MAX77843_MUIC_ADC_RESERVED_ACC_4, but
I don't think it's the only one, that's why it wouldn't be right
to call it e.g. MAX77843_MUIC_ADC_GEAR_VR.

I can of course add a comment on top of the above lines to make
it clearer.

Thanks,
Andi