[PATCH v9 0/4] pinctrl: pinmux: Add pinmux-select debugfs file

[PATCH v9 0/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

This series first converts the debugfs files in the pinctrl subsystem to
octal permissions and then adds a new debugfs file "pinmux-select".

Group name and function name can be written to "pinmux-select" which
will cause the pin function for the specified group to be activated on
the pin controller.

This series also renames documentation from pinctl to pin-control and
adds documentation for the pinctrl debugfs files.

Notes for PATCH v9:
- rename pinctl.rst documentation to pin-control.rst per discussion
  with Linus W.

Notes for PATCH v8:
- add 'Reviewed-by:' from Geert Uytterhoeven for pinmux-select patch
- add 'Tested-by:' from Geert Uytterhoeven for pinmux-select patch
- change pinmux-select format to '<group-name function-name>' based on
  feedback from Geert
- rephrase parts of documentation per Geert's comments

Notes for PATCH v7:
- add 'Reviewed-by:' from Andy Shevchenko for pinmux-select patch
- add 'Reviewed-by:' from Andy Shevchenko for documentation patch
- add 'Reviewed-by:' from Tony Lindgren to all patches
- change order of '#include <linux/ctype.h>' per Andy's suggestion
- change PINMUX_SELECT_MAX back to 128 as I had accidentally changed it
  to 50 and Andy pointed this out.
- grammer fixes as suggested by Andy
- rework assignment of fsel and ret from pinmux_func_name_to_selector()
- rework assignment of gsel and ret from pinctrl_get_group_selector()

Notes for PATCH v6:
- add 'Suggested-by:' for Joe Perches to octal permissions patch
- add 'Reviewed-by:' from Andy and Geert to octal permissions patch
- reword example in the pinmux-select patch per Andy's advice
- indent the example output per Andy's advice
- remove usage error messages as Andy advised it is too verbose
- return -ENOMEM when write is too big for the input buffer per Andy's advice
- handle whitespace before, in between, and after the function name and
  group name as suggested by Andy
- rename free_buf to exit_free_buf per Andy's advice
- add documentation patch to series which documents the debugfs files
  for the pinctrl subsystem including the new pinmux-select file

Notes for PATCH v5:
- convert permissions from symbolic to octal for debugfs_create_file()
  calls in core.c that Joe Perches pointed out I had missed
- Linus W: please let me know if I should break this series apart as you
  already applied an earlier version of octal conversion patch today [1]
- switch from sscanf() to just pointing to function name and group name
  inside of the buffer. This also avoids having to allocate additional
  buffers for fname and gname. Geert and Andy highlighted this security
  issue and Andy suggested code to use instead of sscanf().
- switch from devm_kfree() to kfree() after Dan Carpenter warned me
- remove .read from pinmux_select_ops per Geert since it is write only
- add usage format to error when unable find fname or gname in buffer

Notes for PATCH v4:
- correct the commit message in the second patch to reference function
  and group name instead of integer selectors. Apologies for not fixing
  that in v3
- fix typos in cover letter

Notes for PATCH v3:
- add Suggested-by: Andy Shevchenko to the "pinctrl: use to octal
  permissions for debugfs files" patch
- change the octal permissions from 0400 to 0444 to correctly match the
  symbolic permissions (thanks to Joe Perches and Geert Uytterhoeven)
- note that S_IFREG flag is added to the mode in __debugfs_create_file()
  (thanks to Andy for highlighting this and Joe for suggesting I should
  add a note to the commit message)
- fix order of the goto labels so that the buffers are freed correctly
  as suggested by Dan Carpenter
- move from devm_kzalloc() to kzalloc() as the buffers are only used
  inside the pinmux_select() function and not related to the lifetime
  of the pin controller device (thanks to Andy for pointing this out)
- correct the pinmux-select example in commit message to use the
  function and group name instead of selector (thanks to Geert)

Notes for PATCH v2:
- create patch series that includes patch to switch all the debugfs
  files in pinctrl subsystem over to octal permission
- write function name and group name, instead of error-prone selector
  numbers, to the 'pinmux-select' file
- switch from static to dynamic allocation for the kernel buffer filled
  by strncpy_from_user()
- look up function selector from function name using
  pinmux_func_name_to_selector()
- validate group name with get_function_groups() and match_string()
- look up selector for group name with pinctrl_get_group_selector()

Notes for PATCH v1:
- posted seperate patch to switch all the debugfs files in pinctrl
  subsystem over to octal permission
- there is no existing documentation for any of the debugfs enteries for
  pinctrl, so it seemed to have a bigger scope than just this patch. I
  also noticed that rst documentation is confusingly named "pinctl" (no
  'r') and started thread about that [2]. Linus suggested chaning that
  to 'pin-control'. Thus I am planning a seperate documentation patch
  series where the file is renamed, references changed and a section on
  the pinctrl debugfs files is added.

Notes for RFC v2 [3]:
- rename debugfs file "pinmux-set" to "pinmux-select"
- renmae pinmux_set_write() to pinmux_select()
- switch from memdup_user_nul() to strncpy_from_user()
- switch from pr_warn() to dev_err()

[1] https://lore.kernel.org/linux-gpio/20210126044742.87602-1-drew@beagleboard.org/
[2] https://lore.kernel.org/linux-gpio/20210126050817.GA187797@x1/
[3] https://lore.kernel.org/linux-gpio/20210123064909.466225-1-drew@beagleboard.org/

Drew Fustini (4):
  pinctrl: use to octal permissions for debugfs files
  pinctrl: pinmux: Add pinmux-select debugfs file
  Documentation: rename pinctl to pin-control
  docs/pinctrl: document debugfs files

 Documentation/driver-api/gpio/legacy.rst      |   2 +-
 Documentation/driver-api/index.rst            |   2 +-
 .../{pinctl.rst => pin-control.rst}           |  37 ++++++
 MAINTAINERS                                   |   2 +-
 drivers/pinctrl/core.c                        |  12 +-
 drivers/pinctrl/pinconf.c                     |   4 +-
 drivers/pinctrl/pinmux.c                      | 106 +++++++++++++++++-
 7 files changed, 152 insertions(+), 13 deletions(-)
 rename Documentation/driver-api/{pinctl.rst => pin-control.rst} (97%)

-- 
2.25.1

[PATCH v9 1/4] pinctrl: use to octal permissions for debugfs files

[Drew Fustini]

Switch over pinctrl debugfs files to use octal permissions as they are
preferred over symbolic permissions. Refer to commit f90774e1fd27
("checkpatch: look for symbolic permissions and suggest octal instead").

Note: S_IFREG flag is added to the mode by __debugfs_create_file()
in fs/debugfs/inode.c

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 drivers/pinctrl/core.c    | 12 ++++++------
 drivers/pinctrl/pinconf.c |  4 ++--
 drivers/pinctrl/pinmux.c  |  4 ++--
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 3663d87f51a0..07458742bc0f 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1888,11 +1888,11 @@ static void pinctrl_init_device_debugfs(struct pinctrl_dev *pctldev)
 			dev_name(pctldev->dev));
 		return;
 	}
-	debugfs_create_file("pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pins", 0444,
 			    device_root, pctldev, &pinctrl_pins_fops);
-	debugfs_create_file("pingroups", S_IFREG | S_IRUGO,
+	debugfs_create_file("pingroups", 0444,
 			    device_root, pctldev, &pinctrl_groups_fops);
-	debugfs_create_file("gpio-ranges", S_IFREG | S_IRUGO,
+	debugfs_create_file("gpio-ranges", 0444,
 			    device_root, pctldev, &pinctrl_gpioranges_fops);
 	if (pctldev->desc->pmxops)
 		pinmux_init_device_debugfs(device_root, pctldev);
@@ -1914,11 +1914,11 @@ static void pinctrl_init_debugfs(void)
 		return;
 	}
 
-	debugfs_create_file("pinctrl-devices", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-devices", 0444,
 			    debugfs_root, NULL, &pinctrl_devices_fops);
-	debugfs_create_file("pinctrl-maps", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-maps", 0444,
 			    debugfs_root, NULL, &pinctrl_maps_fops);
-	debugfs_create_file("pinctrl-handles", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinctrl-handles", 0444,
 			    debugfs_root, NULL, &pinctrl_fops);
 }
 
diff --git a/drivers/pinctrl/pinconf.c b/drivers/pinctrl/pinconf.c
index 02c075cc010b..d9d54065472e 100644
--- a/drivers/pinctrl/pinconf.c
+++ b/drivers/pinctrl/pinconf.c
@@ -370,9 +370,9 @@ DEFINE_SHOW_ATTRIBUTE(pinconf_groups);
 void pinconf_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
-	debugfs_create_file("pinconf-pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinconf-pins", 0444,
 			    devroot, pctldev, &pinconf_pins_fops);
-	debugfs_create_file("pinconf-groups", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinconf-groups", 0444,
 			    devroot, pctldev, &pinconf_groups_fops);
 }
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index bab888fe3f8e..c651b2db0925 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -676,9 +676,9 @@ DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
 void pinmux_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
-	debugfs_create_file("pinmux-functions", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinmux-functions", 0444,
 			    devroot, pctldev, &pinmux_functions_fops);
-	debugfs_create_file("pinmux-pins", S_IFREG | S_IRUGO,
+	debugfs_create_file("pinmux-pins", 0444,
 			    devroot, pctldev, &pinmux_pins_fops);
 }
 
-- 
2.25.1

[PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

Add "pinmux-select" to debugfs which will activate a pin function for a
given pin group:

  echo "<group-name function-name>" > pinmux-select

The write operation pinmux_select() handles this by checking that the
names map to valid selectors and then calling ops->set_mux().

The existing "pinmux-functions" debugfs file lists the pin functions
registered for the pin controller. For example:

  function: pinmux-uart0, groups = [ pinmux-uart0-pins ]
  function: pinmux-mmc0, groups = [ pinmux-mmc0-pins ]
  function: pinmux-mmc1, groups = [ pinmux-mmc1-pins ]
  function: pinmux-i2c0, groups = [ pinmux-i2c0-pins ]
  function: pinmux-i2c1, groups = [ pinmux-i2c1-pins ]
  function: pinmux-spi1, groups = [ pinmux-spi1-pins ]

To activate function pinmux-i2c1 on group pinmux-i2c1-pins:

  echo "pinmux-i2c1-pins pinmux-i2c1" > pinmux-select

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 drivers/pinctrl/pinmux.c | 102 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index c651b2db0925..f4abfaecfc5c 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -12,6 +12,7 @@
  */
 #define pr_fmt(fmt) "pinmux core: " fmt
 
+#include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
@@ -673,6 +674,105 @@ void pinmux_show_setting(struct seq_file *s,
 DEFINE_SHOW_ATTRIBUTE(pinmux_functions);
 DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
 
+#define PINMUX_SELECT_MAX 128
+static ssize_t pinmux_select(struct file *file, const char __user *user_buf,
+				   size_t len, loff_t *ppos)
+{
+	struct seq_file *sfile = file->private_data;
+	struct pinctrl_dev *pctldev = sfile->private;
+	const struct pinmux_ops *pmxops = pctldev->desc->pmxops;
+	const char *const *groups;
+	char *buf, *gname, *fname;
+	unsigned int num_groups;
+	int fsel, gsel, ret;
+
+	if (len > PINMUX_SELECT_MAX)
+		return -ENOMEM;
+
+	buf = kzalloc(PINMUX_SELECT_MAX, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = strncpy_from_user(buf, user_buf, PINMUX_SELECT_MAX);
+	if (ret < 0)
+		goto exit_free_buf;
+	buf[len-1] = '\0';
+
+	/* remove leading and trailing spaces of input buffer */
+	gname = strstrip(buf);
+	if (*gname == '\0') {
+		ret = -EINVAL;
+		goto exit_free_buf;
+	}
+
+	/* find a separator which is a spacelike character */
+	for (fname = gname; !isspace(*fname); fname++) {
+		if (*fname == '\0') {
+			ret = -EINVAL;
+			goto exit_free_buf;
+		}
+	}
+	*fname = '\0';
+
+	/* drop extra spaces between function and group names */
+	fname = skip_spaces(fname + 1);
+	if (*fname == '\0') {
+		ret = -EINVAL;
+		goto exit_free_buf;
+	}
+
+	ret = pinmux_func_name_to_selector(pctldev, fname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "invalid function %s in map table\n", fname);
+		goto exit_free_buf;
+	}
+	fsel = ret;
+
+	ret = pmxops->get_function_groups(pctldev, fsel, &groups, &num_groups);
+	if (ret) {
+		dev_err(pctldev->dev, "no groups for function %d (%s)", fsel, fname);
+		goto exit_free_buf;
+	}
+
+	ret = match_string(groups, num_groups, gname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "invalid group %s", gname);
+		goto exit_free_buf;
+	}
+
+	ret = pinctrl_get_group_selector(pctldev, gname);
+	if (ret < 0) {
+		dev_err(pctldev->dev, "failed to get group selector for %s", gname);
+		goto exit_free_buf;
+	}
+	gsel = ret;
+
+	ret = pmxops->set_mux(pctldev, fsel, gsel);
+	if (ret) {
+		dev_err(pctldev->dev, "set_mux() failed: %d", ret);
+		goto exit_free_buf;
+	}
+	ret = len;
+
+exit_free_buf:
+	kfree(buf);
+
+	return ret;
+}
+
+static int pinmux_select_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, NULL, inode->i_private);
+}
+
+static const struct file_operations pinmux_select_ops = {
+	.owner = THIS_MODULE,
+	.open = pinmux_select_open,
+	.write = pinmux_select,
+	.llseek = no_llseek,
+	.release = single_release,
+};
+
 void pinmux_init_device_debugfs(struct dentry *devroot,
 			 struct pinctrl_dev *pctldev)
 {
@@ -680,6 +780,8 @@ void pinmux_init_device_debugfs(struct dentry *devroot,
 			    devroot, pctldev, &pinmux_functions_fops);
 	debugfs_create_file("pinmux-pins", 0444,
 			    devroot, pctldev, &pinmux_pins_fops);
+	debugfs_create_file("pinmux-select", 0200,
+			    devroot, pctldev, &pinmux_select_ops);
 }
 
 #endif /* CONFIG_DEBUG_FS */
-- 
2.25.1

[PATCH v9 3/4] Documentation: rename pinctl to pin-control

[Drew Fustini]

pinctl is not ideal as pinctrl (with an 'r') is much more common. Linus
state that pin-control.rst would be the best name for the documentation.

Link: https://lore.kernel.org/linux-gpio/20210126050817.GA187797@x1/#t
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 Documentation/driver-api/gpio/legacy.rst                 | 2 +-
 Documentation/driver-api/index.rst                       | 2 +-
 Documentation/driver-api/{pinctl.rst => pin-control.rst} | 0
 MAINTAINERS                                              | 2 +-
 4 files changed, 3 insertions(+), 3 deletions(-)
 rename Documentation/driver-api/{pinctl.rst => pin-control.rst} (100%)

diff --git a/Documentation/driver-api/gpio/legacy.rst b/Documentation/driver-api/gpio/legacy.rst
index 9bc34ba697d9..9b12eeb89170 100644
--- a/Documentation/driver-api/gpio/legacy.rst
+++ b/Documentation/driver-api/gpio/legacy.rst
@@ -461,7 +461,7 @@ pin controller?
 
 This is done by registering "ranges" of pins, which are essentially
 cross-reference tables. These are described in
-Documentation/driver-api/pinctl.rst
+Documentation/driver-api/pin-control.rst
 
 While the pin allocation is totally managed by the pinctrl subsystem,
 gpio (under gpiolib) is still maintained by gpio drivers. It may happen
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index f357f3eb400c..cd382bda2cf9 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -60,7 +60,7 @@ available subsections can be seen below.
    80211/index
    uio-howto
    firmware/index
-   pinctl
+   pin-control
    gpio/index
    md/index
    media/index
diff --git a/Documentation/driver-api/pinctl.rst b/Documentation/driver-api/pin-control.rst
similarity index 100%
rename from Documentation/driver-api/pinctl.rst
rename to Documentation/driver-api/pin-control.rst
diff --git a/MAINTAINERS b/MAINTAINERS
index 281de213ef47..c54c98910dd4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13800,7 +13800,7 @@ L:	linux-gpio@vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git
 F:	Documentation/devicetree/bindings/pinctrl/
-F:	Documentation/driver-api/pinctl.rst
+F:	Documentation/driver-api/pin-control.rst
 F:	drivers/pinctrl/
 F:	include/linux/pinctrl/
 
-- 
2.25.1

[PATCH v9 4/4] docs/pinctrl: document debugfs files

[Drew Fustini]

Document debugfs directories and files created for pinctrl subsystem.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Drew Fustini <drew@beagleboard.org>
---
 Documentation/driver-api/pin-control.rst | 37 ++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst
index 3d2deaf48841..c905b273e833 100644
--- a/Documentation/driver-api/pin-control.rst
+++ b/Documentation/driver-api/pin-control.rst
@@ -1428,3 +1428,40 @@ on the pins defined by group B::
 The above has to be done from process context. The reservation of the pins
 will be done when the state is activated, so in effect one specific pin
 can be used by different functions at different times on a running system.
+
+
+Debugfs files
+=============
+These files are created in ``/sys/kernel/debug/pinctrl``:
+
+- ``pinctrl-devices``: prints each pin controller device along with columns to
+  indicate support for pinmux and pinconf
+
+- ``pinctrl-handles``: prints each configured pin controller handle and the
+  corresponding pinmux maps
+
+- ``pinctrl-maps``: print all pinctrl maps
+
+A sub-directory is created inside of ``/sys/kernel/debug/pinctrl`` for each pin
+controller device containing these files:
+
+- ``pins``: prints a line for each pin registered on the pin controller. The
+  pinctrl driver may add additional information such as register contents.
+
+- ``gpio-ranges``: print ranges that map gpio lines to pins on the controller
+
+- ``pingroups``: print all pin groups registered on the pin controller
+
+- ``pinconf-pins``: print pin config settings for each pin
+
+- ``pinconf-groups``: print pin config settings per pin group
+
+- ``pinmux-functions``: print each pin function along with the pin groups that
+  map to the pin function
+
+- ``pinmux-pins``: iterate through all pins and print mux owner, gpio owner
+  and if the pin is a hog
+
+- ``pinmux-select``: write to this file to activate a pin function for a group::
+
+        echo "<group-name function-name>" > pinmux-select
-- 
2.25.1

Re: [PATCH v9 0/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Linus Walleij]

On Tue, Mar 2, 2021 at 6:32 AM Drew Fustini <drew@beagleboard.org> wrote:

> This series first converts the debugfs files in the pinctrl subsystem to
> octal permissions and then adds a new debugfs file "pinmux-select".
>
> Group name and function name can be written to "pinmux-select" which
> will cause the pin function for the specified group to be activated on
> the pin controller.
>
> This series also renames documentation from pinctl to pin-control and
> adds documentation for the pinctrl debugfs files.
>
> Notes for PATCH v9:
> - rename pinctl.rst documentation to pin-control.rst per discussion
>   with Linus W.

Excellent, I have applied this v9 version!

Good job!
Linus Walleij

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Enrico Weigelt, metux IT consult]

On 02.03.21 06:30, Drew Fustini wrote:

Hi folks,

> Add "pinmux-select" to debugfs which will activate a pin function for a
> given pin group:
> 
>    echo "<group-name function-name>" > pinmux-select
> 
> The write operation pinmux_select() handles this by checking that the
> names map to valid selectors and then calling ops->set_mux().

I've already been playing with similar idea, but for external muxes.
For example, some boards have multiple SIM slots that can be switched
via some gpio pin.

Not sure whether traditional pinmux would be a good match for that.


--mtx

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info@metux.net -- +49-151-27565287

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini]

On Fri, Mar 12, 2021 at 02:57:54PM +0100, Enrico Weigelt, metux IT consult wrote:
> On 02.03.21 06:30, Drew Fustini wrote:
> 
> Hi folks,
> 
> > Add "pinmux-select" to debugfs which will activate a pin function for a
> > given pin group:
> > 
> >    echo "<group-name function-name>" > pinmux-select
> > 
> > The write operation pinmux_select() handles this by checking that the
> > names map to valid selectors and then calling ops->set_mux().
> 
> I've already been playing with similar idea, but for external muxes.
> For example, some boards have multiple SIM slots that can be switched
> via some gpio pin.
> 
> Not sure whether traditional pinmux would be a good match for that.
> 
> 
> --mtx
> 

Thank you for your comment.  I am interested in understanding other
use cases.

Linus can hopefully correct me, but I think this is covered by section
"Drivers needing both pin control and GPIOs" in pinctl.rst [1]. The
driver could be both a GPIO consumer and pinctrl consumer and then be
able to call pinctrl_select_state() and devm_gpio_request().

Thank you,
Drew

[1] https://www.kernel.org/doc/html/latest/driver-api/pinctl.html

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Alexandre Belloni]

On 12/03/2021 14:57:54+0100, Enrico Weigelt, metux IT consult wrote:
> On 02.03.21 06:30, Drew Fustini wrote:
> 
> Hi folks,
> 
> > Add "pinmux-select" to debugfs which will activate a pin function for a
> > given pin group:
> > 
> >    echo "<group-name function-name>" > pinmux-select
> > 
> > The write operation pinmux_select() handles this by checking that the
> > names map to valid selectors and then calling ops->set_mux().
> 
> I've already been playing with similar idea, but for external muxes.
> For example, some boards have multiple SIM slots that can be switched
> via some gpio pin.
> 
> Not sure whether traditional pinmux would be a good match for that.
> 

If you want to be able to use both, then I guess gpio-mux is what you
are looking for. Obviously, it will also require support in the bus
core. On what bus are those SIMs? (I guess the answer will be UART and
then unfortunately UARTs are not represented as busses).


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Geert Uytterhoeven]

Hi Alexandre,

On Sat, Mar 13, 2021 at 10:28 AM Alexandre Belloni
<alexandre.belloni@bootlin.com> wrote:
> On 12/03/2021 14:57:54+0100, Enrico Weigelt, metux IT consult wrote:
> > On 02.03.21 06:30, Drew Fustini wrote:
> > > Add "pinmux-select" to debugfs which will activate a pin function for a
> > > given pin group:
> > >
> > >    echo "<group-name function-name>" > pinmux-select
> > >
> > > The write operation pinmux_select() handles this by checking that the
> > > names map to valid selectors and then calling ops->set_mux().
> >
> > I've already been playing with similar idea, but for external muxes.
> > For example, some boards have multiple SIM slots that can be switched
> > via some gpio pin.
> >
> > Not sure whether traditional pinmux would be a good match for that.
>
> If you want to be able to use both, then I guess gpio-mux is what you
> are looking for. Obviously, it will also require support in the bus
> core. On what bus are those SIMs? (I guess the answer will be UART and
> then unfortunately UARTs are not represented as busses).

We do have support for devices connected to UARTs.
See patternProperties in Documentation/devicetree/bindings/serial/serial.yaml.
Or do you mean something different?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Linus Walleij]

On Fri, Mar 12, 2021 at 2:57 PM Enrico Weigelt, metux IT consult
<lkml@metux.net> wrote:
> On 02.03.21 06:30, Drew Fustini wrote:
>
> Hi folks,
>
> > Add "pinmux-select" to debugfs which will activate a pin function for a
> > given pin group:
> >
> >    echo "<group-name function-name>" > pinmux-select
> >
> > The write operation pinmux_select() handles this by checking that the
> > names map to valid selectors and then calling ops->set_mux().
>
> I've already been playing with similar idea, but for external muxes.
> For example, some boards have multiple SIM slots that can be switched
> via some gpio pin.
>
> Not sure whether traditional pinmux would be a good match for that.

What is wrong with the subsystem
drivers/mux?

It's exactly for this usecase I think. Peter Rosin already wrote
a GPIO-controlled mux driver too.

Yours,
Linus Walleij

Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

[Enrico Weigelt, metux IT consult]

On 13.03.21 19:47, Geert Uytterhoeven wrote:

>>> I've already been playing with similar idea, but for external muxes.
>>> For example, some boards have multiple SIM slots that can be switched
>>> via some gpio pin.
>>>
>>> Not sure whether traditional pinmux would be a good match for that.
>>
>> If you want to be able to use both, then I guess gpio-mux is what you
>> are looking for. Obviously, it will also require support in the bus
>> core. On what bus are those SIMs? (I guess the answer will be UART and
>> then unfortunately UARTs are not represented as busses).
> 
> We do have support for devices connected to UARTs.
> See patternProperties in Documentation/devicetree/bindings/serial/serial.yaml.
> Or do you mean something different?

in my case, the SIM cards are connected directly to the baseband
(there're extra lines on the m2 slots for that). CPU doesn't ever see
any of this traffic, just can select which SIM card is routed to the
m2 slot via gpio.


--mtx

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