[PATCH v5 0/2] Read _SUB from ACPI to be able to identify firmware

[PATCH v5 0/2] Read _SUB from ACPI to be able to identify firmware

[Stefan Binding]

CS35L41 has a DSP which is able to run firmware, as well as a tuning file.
Different systems may want to use different firmwares and tuning files, and
some firmwares/tunings may not be compatible with other systems.
To allow a system to select the correct fimware/tuning, we can read an _SUB
from the ACPI. This _SUB can then be used to uniquely identify the system
in the firmware/tuning file name.

Add a helper function which reads the _SUB, so this can be used by other
parts in the future.
Add support inside the CS35L41 ASoC driver to read this _SUB, and save it
appropriately.

Changes since v4:
- Rename function

Changes since v3:
- Fix 32 bit format string warning

Changes since v2:
- Fix error in function prototype

Changes since v1:
- Add length validation for SSID String
- Rename API
- Allocate memory inside API
- Use ACPI_HANDLE macro instead of ACPI_COMPANION
- Improve error handling

Stefan Binding (2):
  ACPI: utils: Add api to read _SUB from ACPI
  ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

 drivers/acpi/utils.c       | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h       |  6 ++++++
 sound/soc/codecs/cs35l41.c | 24 ++++++++++++++++++++++++
 3 files changed, 68 insertions(+)

-- 
2.25.1

[PATCH v5 0/2] Read _SUB from ACPI to be able to identify firmware

[Stefan Binding]

CS35L41 has a DSP which is able to run firmware, as well as a tuning file.
Different systems may want to use different firmwares and tuning files, and
some firmwares/tunings may not be compatible with other systems.
To allow a system to select the correct fimware/tuning, we can read an _SUB
from the ACPI. This _SUB can then be used to uniquely identify the system
in the firmware/tuning file name.

Add a helper function which reads the _SUB, so this can be used by other
parts in the future.
Add support inside the CS35L41 ASoC driver to read this _SUB, and save it
appropriately.

Changes since v4:
- Rename function

Changes since v3:
- Fix 32 bit format string warning

Changes since v2:
- Fix error in function prototype

Changes since v1:
- Add length validation for SSID String
- Rename API
- Allocate memory inside API
- Use ACPI_HANDLE macro instead of ACPI_COMPANION
- Improve error handling

Stefan Binding (2):
  ACPI: utils: Add api to read _SUB from ACPI
  ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

 drivers/acpi/utils.c       | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h       |  6 ++++++
 sound/soc/codecs/cs35l41.c | 24 ++++++++++++++++++++++++
 3 files changed, 68 insertions(+)

-- 
2.25.1

[PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Stefan Binding]

Add a wrapper function to read the _SUB string from ACPI.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
 drivers/acpi/utils.c | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h |  6 ++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 3a9773a09e19..394954f4b6ef 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -291,6 +291,44 @@ int acpi_get_local_address(acpi_handle handle, u32 *addr)
 }
 EXPORT_SYMBOL(acpi_get_local_address);
 
+#define ACPI_MAX_SUB_BUF_SIZE	9
+
+const char *acpi_get_subsystem_id(acpi_handle handle)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	acpi_status status;
+	const char *sub;
+
+	status = acpi_evaluate_object(handle, METHOD_NAME__SUB, NULL, &buffer);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_debug(handle, "Reading ACPI _SUB failed: %#x\n", status);
+		return ERR_PTR(-ENODATA);
+	}
+
+	obj = buffer.pointer;
+	if (obj->type == ACPI_TYPE_STRING) {
+		if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
+		    strlen(obj->string.pointer) > 0) {
+			sub = kstrdup(obj->string.pointer, GFP_KERNEL);
+			if (!sub)
+				sub = ERR_PTR(-ENOMEM);
+		} else {
+			acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
+					strlen(obj->string.pointer));
+			sub = ERR_PTR(-EINVAL);
+		}
+	} else {
+		acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
+		sub = ERR_PTR(-EINVAL);
+	}
+
+	acpi_os_free(buffer.pointer);
+
+	return sub;
+}
+EXPORT_SYMBOL_GPL(acpi_get_subsystem_id);
+
 acpi_status
 acpi_evaluate_reference(acpi_handle handle,
 			acpi_string pathname,
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 7b96a8bff6d2..7651198ad6f5 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -762,6 +762,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
 #endif
 
 int acpi_get_local_address(acpi_handle handle, u32 *addr);
+const char *acpi_get_subsystem_id(acpi_handle handle);
 
 #else	/* !CONFIG_ACPI */
 
@@ -1023,6 +1024,11 @@ static inline int acpi_get_local_address(acpi_handle handle, u32 *addr)
 	return -ENODEV;
 }
 
+static inline const char *acpi_get_subsystem_id(acpi_handle handle)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline int acpi_register_wakeup_handler(int wake_irq,
 	bool (*wakeup)(void *context), void *context)
 {
-- 
2.25.1

[PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Stefan Binding]

Add a wrapper function to read the _SUB string from ACPI.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
 drivers/acpi/utils.c | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h |  6 ++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 3a9773a09e19..394954f4b6ef 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -291,6 +291,44 @@ int acpi_get_local_address(acpi_handle handle, u32 *addr)
 }
 EXPORT_SYMBOL(acpi_get_local_address);
 
+#define ACPI_MAX_SUB_BUF_SIZE	9
+
+const char *acpi_get_subsystem_id(acpi_handle handle)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	acpi_status status;
+	const char *sub;
+
+	status = acpi_evaluate_object(handle, METHOD_NAME__SUB, NULL, &buffer);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_debug(handle, "Reading ACPI _SUB failed: %#x\n", status);
+		return ERR_PTR(-ENODATA);
+	}
+
+	obj = buffer.pointer;
+	if (obj->type == ACPI_TYPE_STRING) {
+		if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
+		    strlen(obj->string.pointer) > 0) {
+			sub = kstrdup(obj->string.pointer, GFP_KERNEL);
+			if (!sub)
+				sub = ERR_PTR(-ENOMEM);
+		} else {
+			acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
+					strlen(obj->string.pointer));
+			sub = ERR_PTR(-EINVAL);
+		}
+	} else {
+		acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
+		sub = ERR_PTR(-EINVAL);
+	}
+
+	acpi_os_free(buffer.pointer);
+
+	return sub;
+}
+EXPORT_SYMBOL_GPL(acpi_get_subsystem_id);
+
 acpi_status
 acpi_evaluate_reference(acpi_handle handle,
 			acpi_string pathname,
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 7b96a8bff6d2..7651198ad6f5 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -762,6 +762,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
 #endif
 
 int acpi_get_local_address(acpi_handle handle, u32 *addr);
+const char *acpi_get_subsystem_id(acpi_handle handle);
 
 #else	/* !CONFIG_ACPI */
 
@@ -1023,6 +1024,11 @@ static inline int acpi_get_local_address(acpi_handle handle, u32 *addr)
 	return -ENODEV;
 }
 
+static inline const char *acpi_get_subsystem_id(acpi_handle handle)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline int acpi_register_wakeup_handler(int wake_irq,
 	bool (*wakeup)(void *context), void *context)
 {
-- 
2.25.1

[PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Stefan Binding]

When loading firmware, wm_adsp uses a number of parameters to
determine the path of the firmware and tuning files to load.
One of these parameters is system_name.
Add support in cs35l41 to read this system name from the ACPI
_SUB ID in order to uniquely identify the firmware and tuning
mapped to a particular system.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
 sound/soc/codecs/cs35l41.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/sound/soc/codecs/cs35l41.c b/sound/soc/codecs/cs35l41.c
index 8766e19d85f1..d70469686699 100644
--- a/sound/soc/codecs/cs35l41.c
+++ b/sound/soc/codecs/cs35l41.c
@@ -6,6 +6,7 @@
 //
 // Author: David Rhodes <david.rhodes@cirrus.com>
 
+#include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -1142,6 +1143,24 @@ static int cs35l41_dsp_init(struct cs35l41_private *cs35l41)
 	return ret;
 }
 
+static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
+{
+	acpi_handle handle = ACPI_HANDLE(cs35l41->dev);
+	const char *sub;
+
+	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
+	if (!handle)
+		return 0;
+
+	sub = acpi_get_subsystem_id(handle);
+	if (IS_ERR(sub))
+		return PTR_ERR(sub);
+
+	cs35l41->dsp.system_name = sub;
+	dev_dbg(cs35l41->dev, "Susystem ID: %s\n", cs35l41->dsp.system_name);
+	return 0;
+}
+
 int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *hw_cfg)
 {
 	u32 regid, reg_revid, i, mtl_revid, int_status, chipid_match;
@@ -1270,6 +1289,10 @@ int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *
 		goto err;
 	}
 
+	ret = cs35l41_acpi_get_name(cs35l41);
+	if (ret < 0)
+		goto err;
+
 	ret = cs35l41_dsp_init(cs35l41);
 	if (ret < 0)
 		goto err;
@@ -1316,6 +1339,7 @@ void cs35l41_remove(struct cs35l41_private *cs35l41)
 	pm_runtime_disable(cs35l41->dev);
 
 	regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF);
+	kfree(cs35l41->dsp.system_name);
 	wm_adsp2_remove(&cs35l41->dsp);
 	cs35l41_safe_reset(cs35l41->regmap, cs35l41->hw_cfg.bst_type);
 
-- 
2.25.1

[PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Stefan Binding]

When loading firmware, wm_adsp uses a number of parameters to
determine the path of the firmware and tuning files to load.
One of these parameters is system_name.
Add support in cs35l41 to read this system name from the ACPI
_SUB ID in order to uniquely identify the firmware and tuning
mapped to a particular system.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
 sound/soc/codecs/cs35l41.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/sound/soc/codecs/cs35l41.c b/sound/soc/codecs/cs35l41.c
index 8766e19d85f1..d70469686699 100644
--- a/sound/soc/codecs/cs35l41.c
+++ b/sound/soc/codecs/cs35l41.c
@@ -6,6 +6,7 @@
 //
 // Author: David Rhodes <david.rhodes@cirrus.com>
 
+#include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -1142,6 +1143,24 @@ static int cs35l41_dsp_init(struct cs35l41_private *cs35l41)
 	return ret;
 }
 
+static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
+{
+	acpi_handle handle = ACPI_HANDLE(cs35l41->dev);
+	const char *sub;
+
+	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
+	if (!handle)
+		return 0;
+
+	sub = acpi_get_subsystem_id(handle);
+	if (IS_ERR(sub))
+		return PTR_ERR(sub);
+
+	cs35l41->dsp.system_name = sub;
+	dev_dbg(cs35l41->dev, "Susystem ID: %s\n", cs35l41->dsp.system_name);
+	return 0;
+}
+
 int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *hw_cfg)
 {
 	u32 regid, reg_revid, i, mtl_revid, int_status, chipid_match;
@@ -1270,6 +1289,10 @@ int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *
 		goto err;
 	}
 
+	ret = cs35l41_acpi_get_name(cs35l41);
+	if (ret < 0)
+		goto err;
+
 	ret = cs35l41_dsp_init(cs35l41);
 	if (ret < 0)
 		goto err;
@@ -1316,6 +1339,7 @@ void cs35l41_remove(struct cs35l41_private *cs35l41)
 	pm_runtime_disable(cs35l41->dev);
 
 	regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF);
+	kfree(cs35l41->dsp.system_name);
 	wm_adsp2_remove(&cs35l41->dsp);
 	cs35l41_safe_reset(cs35l41->regmap, cs35l41->hw_cfg.bst_type);
 
-- 
2.25.1

Re: [PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Pierre-Louis Bossart]

On 6/30/22 10:01, Stefan Binding wrote:
> When loading firmware, wm_adsp uses a number of parameters to
> determine the path of the firmware and tuning files to load.
> One of these parameters is system_name.
> Add support in cs35l41 to read this system name from the ACPI
> _SUB ID in order to uniquely identify the firmware and tuning
> mapped to a particular system.

It's my understanding that the _SUB method is optional, not required. It
may be wise to plan for a fallback, e.g to use DMI quirks or other
identifiers, no?

If it's used quite widely, then it may be a good thing to add to
'alsa-info'.
> Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
> ---
>  sound/soc/codecs/cs35l41.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/sound/soc/codecs/cs35l41.c b/sound/soc/codecs/cs35l41.c
> index 8766e19d85f1..d70469686699 100644
> --- a/sound/soc/codecs/cs35l41.c
> +++ b/sound/soc/codecs/cs35l41.c
> @@ -6,6 +6,7 @@
>  //
>  // Author: David Rhodes <david.rhodes@cirrus.com>
>  
> +#include <linux/acpi.h>
>  #include <linux/delay.h>
>  #include <linux/err.h>
>  #include <linux/init.h>
> @@ -1142,6 +1143,24 @@ static int cs35l41_dsp_init(struct cs35l41_private *cs35l41)
>  	return ret;
>  }
>  
> +static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
> +{
> +	acpi_handle handle = ACPI_HANDLE(cs35l41->dev);
> +	const char *sub;
> +
> +	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
> +	if (!handle)
> +		return 0;
> +
> +	sub = acpi_get_subsystem_id(handle);
> +	if (IS_ERR(sub))
> +		return PTR_ERR(sub);
> +
> +	cs35l41->dsp.system_name = sub;
> +	dev_dbg(cs35l41->dev, "Susystem ID: %s\n", cs35l41->dsp.system_name);

Typo: Subsystem

> +	return 0;
> +}
> +
>  int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *hw_cfg)
>  {
>  	u32 regid, reg_revid, i, mtl_revid, int_status, chipid_match;
> @@ -1270,6 +1289,10 @@ int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *
>  		goto err;
>  	}
>  
> +	ret = cs35l41_acpi_get_name(cs35l41);
> +	if (ret < 0)
> +		goto err;
> +
>  	ret = cs35l41_dsp_init(cs35l41);
>  	if (ret < 0)
>  		goto err;
> @@ -1316,6 +1339,7 @@ void cs35l41_remove(struct cs35l41_private *cs35l41)
>  	pm_runtime_disable(cs35l41->dev);
>  
>  	regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF);
> +	kfree(cs35l41->dsp.system_name);
>  	wm_adsp2_remove(&cs35l41->dsp);
>  	cs35l41_safe_reset(cs35l41->regmap, cs35l41->hw_cfg.bst_type);
>  

Re: [PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Mark Brown]

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On Thu, Jun 30, 2022 at 01:35:05PM -0500, Pierre-Louis Bossart wrote:

> It's my understanding that the _SUB method is optional, not required. It
> may be wise to plan for a fallback, e.g to use DMI quirks or other
> identifiers, no?

Presumably the fallback would go into cs35l41_acpi_get_name()?

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Re: [PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Mark Brown]

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On Thu, Jun 30, 2022 at 01:35:05PM -0500, Pierre-Louis Bossart wrote:

> It's my understanding that the _SUB method is optional, not required. It
> may be wise to plan for a fallback, e.g to use DMI quirks or other
> identifiers, no?

Presumably the fallback would go into cs35l41_acpi_get_name()?

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Re: [PATCH v5 2/2] ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

[Pierre-Louis Bossart]

On 6/30/22 14:34, Mark Brown wrote:
> On Thu, Jun 30, 2022 at 01:35:05PM -0500, Pierre-Louis Bossart wrote:
> 
>> It's my understanding that the _SUB method is optional, not required. It
>> may be wise to plan for a fallback, e.g to use DMI quirks or other
>> identifiers, no?
> 
> Presumably the fallback would go into cs35l41_acpi_get_name()?

That's what I had in mind, if this _SUB does not exist then you could
use something else instead of returning -ENODATA;

+	sub = acpi_get_subsystem_id(handle);
+	if (IS_ERR(sub))
+		return PTR_ERR(sub);
+
+	cs35l41->dsp.system_name = sub;

Re: [PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Rafael J. Wysocki]

On Thu, Jun 30, 2022 at 5:01 PM Stefan Binding
<sbinding@opensource.cirrus.com> wrote:
>
> Add a wrapper function to read the _SUB string from ACPI.
>
> Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
> ---
>  drivers/acpi/utils.c | 38 ++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h |  6 ++++++
>  2 files changed, 44 insertions(+)
>
> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> index 3a9773a09e19..394954f4b6ef 100644
> --- a/drivers/acpi/utils.c
> +++ b/drivers/acpi/utils.c
> @@ -291,6 +291,44 @@ int acpi_get_local_address(acpi_handle handle, u32 *addr)
>  }
>  EXPORT_SYMBOL(acpi_get_local_address);
>
> +#define ACPI_MAX_SUB_BUF_SIZE  9
> +
> +const char *acpi_get_subsystem_id(acpi_handle handle)
> +{
> +       struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +       union acpi_object *obj;
> +       acpi_status status;
> +       const char *sub;
> +
> +       status = acpi_evaluate_object(handle, METHOD_NAME__SUB, NULL, &buffer);
> +       if (ACPI_FAILURE(status)) {
> +               acpi_handle_debug(handle, "Reading ACPI _SUB failed: %#x\n", status);
> +               return ERR_PTR(-ENODATA);
> +       }
> +
> +       obj = buffer.pointer;
> +       if (obj->type == ACPI_TYPE_STRING) {
> +               if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
> +                   strlen(obj->string.pointer) > 0) {
> +                       sub = kstrdup(obj->string.pointer, GFP_KERNEL);
> +                       if (!sub)
> +                               sub = ERR_PTR(-ENOMEM);

The error codes below are somewhat questionable.

> +               } else {
> +                       acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
> +                                       strlen(obj->string.pointer));
> +                       sub = ERR_PTR(-EINVAL);

This is as good as failure, so why not use -ENODATA here?

> +               }
> +       } else {
> +               acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
> +               sub = ERR_PTR(-EINVAL);

Likewise.

> +       }
> +
> +       acpi_os_free(buffer.pointer);
> +
> +       return sub;
> +}
> +EXPORT_SYMBOL_GPL(acpi_get_subsystem_id);
> +
>  acpi_status
>  acpi_evaluate_reference(acpi_handle handle,
>                         acpi_string pathname,
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 7b96a8bff6d2..7651198ad6f5 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -762,6 +762,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
>  #endif
>
>  int acpi_get_local_address(acpi_handle handle, u32 *addr);
> +const char *acpi_get_subsystem_id(acpi_handle handle);
>
>  #else  /* !CONFIG_ACPI */
>
> @@ -1023,6 +1024,11 @@ static inline int acpi_get_local_address(acpi_handle handle, u32 *addr)
>         return -ENODEV;
>  }
>
> +static inline const char *acpi_get_subsystem_id(acpi_handle handle)
> +{
> +       return ERR_PTR(-ENODEV);
> +}
> +
>  static inline int acpi_register_wakeup_handler(int wake_irq,
>         bool (*wakeup)(void *context), void *context)
>  {
> --
> 2.25.1
>

Re: [PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Rafael J. Wysocki]

On Thu, Jun 30, 2022 at 5:01 PM Stefan Binding
<sbinding@opensource.cirrus.com> wrote:
>
> Add a wrapper function to read the _SUB string from ACPI.
>
> Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
> ---
>  drivers/acpi/utils.c | 38 ++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h |  6 ++++++
>  2 files changed, 44 insertions(+)
>
> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> index 3a9773a09e19..394954f4b6ef 100644
> --- a/drivers/acpi/utils.c
> +++ b/drivers/acpi/utils.c
> @@ -291,6 +291,44 @@ int acpi_get_local_address(acpi_handle handle, u32 *addr)
>  }
>  EXPORT_SYMBOL(acpi_get_local_address);
>
> +#define ACPI_MAX_SUB_BUF_SIZE  9
> +
> +const char *acpi_get_subsystem_id(acpi_handle handle)
> +{
> +       struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +       union acpi_object *obj;
> +       acpi_status status;
> +       const char *sub;
> +
> +       status = acpi_evaluate_object(handle, METHOD_NAME__SUB, NULL, &buffer);
> +       if (ACPI_FAILURE(status)) {
> +               acpi_handle_debug(handle, "Reading ACPI _SUB failed: %#x\n", status);
> +               return ERR_PTR(-ENODATA);
> +       }
> +
> +       obj = buffer.pointer;
> +       if (obj->type == ACPI_TYPE_STRING) {
> +               if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
> +                   strlen(obj->string.pointer) > 0) {
> +                       sub = kstrdup(obj->string.pointer, GFP_KERNEL);
> +                       if (!sub)
> +                               sub = ERR_PTR(-ENOMEM);

The error codes below are somewhat questionable.

> +               } else {
> +                       acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
> +                                       strlen(obj->string.pointer));
> +                       sub = ERR_PTR(-EINVAL);

This is as good as failure, so why not use -ENODATA here?

> +               }
> +       } else {
> +               acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
> +               sub = ERR_PTR(-EINVAL);

Likewise.

> +       }
> +
> +       acpi_os_free(buffer.pointer);
> +
> +       return sub;
> +}
> +EXPORT_SYMBOL_GPL(acpi_get_subsystem_id);
> +
>  acpi_status
>  acpi_evaluate_reference(acpi_handle handle,
>                         acpi_string pathname,
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 7b96a8bff6d2..7651198ad6f5 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -762,6 +762,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
>  #endif
>
>  int acpi_get_local_address(acpi_handle handle, u32 *addr);
> +const char *acpi_get_subsystem_id(acpi_handle handle);
>
>  #else  /* !CONFIG_ACPI */
>
> @@ -1023,6 +1024,11 @@ static inline int acpi_get_local_address(acpi_handle handle, u32 *addr)
>         return -ENODEV;
>  }
>
> +static inline const char *acpi_get_subsystem_id(acpi_handle handle)
> +{
> +       return ERR_PTR(-ENODEV);
> +}
> +
>  static inline int acpi_register_wakeup_handler(int wake_irq,
>         bool (*wakeup)(void *context), void *context)
>  {
> --
> 2.25.1
>

Re: [PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Andy Shevchenko]

On Thu, Jun 30, 2022 at 5:17 PM Stefan Binding
<sbinding@opensource.cirrus.com> wrote:
>
> Add a wrapper function to read the _SUB string from ACPI.

...

> +       if (obj->type == ACPI_TYPE_STRING) {
> +               if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
> +                   strlen(obj->string.pointer) > 0) {
> +                       sub = kstrdup(obj->string.pointer, GFP_KERNEL);
> +                       if (!sub)
> +                               sub = ERR_PTR(-ENOMEM);
> +               } else {
> +                       acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
> +                                       strlen(obj->string.pointer));

Three times to evaluate strlen()... Can we do better, please?

> +                       sub = ERR_PTR(-EINVAL);
> +               }
> +       } else {
> +               acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
> +               sub = ERR_PTR(-EINVAL);
> +       }

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v5 1/2] ACPI: utils: Add api to read _SUB from ACPI

[Andy Shevchenko]

On Thu, Jun 30, 2022 at 5:17 PM Stefan Binding
<sbinding@opensource.cirrus.com> wrote:
>
> Add a wrapper function to read the _SUB string from ACPI.

...

> +       if (obj->type == ACPI_TYPE_STRING) {
> +               if (strlen(obj->string.pointer) < ACPI_MAX_SUB_BUF_SIZE &&
> +                   strlen(obj->string.pointer) > 0) {
> +                       sub = kstrdup(obj->string.pointer, GFP_KERNEL);
> +                       if (!sub)
> +                               sub = ERR_PTR(-ENOMEM);
> +               } else {
> +                       acpi_handle_err(handle, "ACPI _SUB Length %zu is Invalid\n",
> +                                       strlen(obj->string.pointer));

Three times to evaluate strlen()... Can we do better, please?

> +                       sub = ERR_PTR(-EINVAL);
> +               }
> +       } else {
> +               acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
> +               sub = ERR_PTR(-EINVAL);
> +       }

-- 
With Best Regards,
Andy Shevchenko