diff mbox series

[v4,1/3] auxdisplay: Add 7-segment LED display driver

Message ID 20240305035853.916430-2-chris.packham@alliedtelesis.co.nz (mailing list archive)
State New, archived
Headers show
Series auxdisplay: 7-segment LED display | expand

Commit Message

Chris Packham March 5, 2024, 3:58 a.m. UTC 
Add a driver for a 7-segment LED display. At the moment only one
character is supported but it should be possible to expand this to
support more characters and/or 14-segment displays in the future.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
    Changes in v4:
    - Fix one more usage of 7 segment
    - Move ASCII art diagram to DT binding
    - Include map_to_7segment.h for map_to_seg7()
    - Use initialiser for values in seg_led_update
    Changes in v3:
    - "7 segment" -> "7-Segment" in Kconfig help text
    - Update after feedback from Andy
    - Use compatible = "gpio-7-segment" as suggested by Rob
    Changes in v2:
    - Rebased on top of auxdisplay/for-next dropping unnecessary code for 7
      segment maps.
    - Update for new linedisp_register() API
    - Include headers based on actual usage
    - Allow building as module
    - Use compatible = "generic-gpio-7seg" to keep checkpatch.pl happy

 drivers/auxdisplay/Kconfig        |  10 +++
 drivers/auxdisplay/Makefile       |   1 +
 drivers/auxdisplay/seg-led-gpio.c | 109 ++++++++++++++++++++++++++++++
 3 files changed, 120 insertions(+)
 create mode 100644 drivers/auxdisplay/seg-led-gpio.c

Comments

Geert Uytterhoeven March 5, 2024, 8:14 a.m. UTC | #1 
Hi Chris,

On Tue, Mar 5, 2024 at 4:59 AM Chris Packham
<chris.packham@alliedtelesis.co.nz> wrote:
> Add a driver for a 7-segment LED display. At the moment only one
> character is supported but it should be possible to expand this to
> support more characters and/or 14-segment displays in the future.
>
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> ---
>
> Notes:
>     Changes in v4:
>     - Fix one more usage of 7 segment
>     - Move ASCII art diagram to DT binding
>     - Include map_to_7segment.h for map_to_seg7()
>     - Use initialiser for values in seg_led_update

Thanks for the update!

> --- a/drivers/auxdisplay/Kconfig
> +++ b/drivers/auxdisplay/Kconfig
> @@ -211,6 +211,16 @@ config ARM_CHARLCD
>           line and the Linux version on the second line, but that's
>           still useful.
>
> +config SEG_LED_GPIO
> +       tristate "Generic 7-segment LED display"

"depends on GPIOLIB || COMPILE_TEST"?

The rest LGTM, so
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert
Geert Uytterhoeven March 5, 2024, 8:23 a.m. UTC | #2 
Hi Chris,

On Tue, Mar 5, 2024 at 4:59 AM Chris Packham
<chris.packham@alliedtelesis.co.nz> wrote:
> Add a driver for a 7-segment LED display. At the moment only one
> character is supported but it should be possible to expand this to
> support more characters and/or 14-segment displays in the future.
>
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>

Sorry, I spoke too soon...

> --- /dev/null
> +++ b/drivers/auxdisplay/seg-led-gpio.c

> +static void seg_led_update(struct work_struct *work)
> +{
> +       struct seg_led_priv *priv = container_of(work, struct seg_led_priv, work.work);
> +       struct linedisp *linedisp = &priv->linedisp;
> +       struct linedisp_map *map = linedisp->map;
> +       DECLARE_BITMAP(values, 8) = { 0 };
> +
> +       bitmap_set_value8(values, map_to_seg7(&map->map.seg7, linedisp->buf[0]), 0);
> +
> +       gpiod_set_array_value_cansleep(priv->segment_gpios->ndescs, priv->segment_gpios->desc,
> +                                      priv->segment_gpios->info, values);
> +}

> +static int seg_led_probe(struct platform_device *pdev)
> +{
> +       struct seg_led_priv *priv;
> +       struct device *dev = &pdev->dev;
> +
> +       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +       if (!priv)
> +               return -ENOMEM;
> +
> +       platform_set_drvdata(pdev, priv);
> +
> +       priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
> +       if (IS_ERR(priv->segment_gpios))
> +               return PTR_ERR(priv->segment_gpios);

This needs some validation of priv->segment_gpios->ndescs, else the
call to gpiod_set_array_value_cansleep() in seg_led_update() may
trigger an out-of-bounds access of the values bitmap.

> +
> +       return linedisp_register(&priv->linedisp, dev, 1, &seg_led_linedisp_ops);
> +}

Gr{oetje,eeting}s,

                        Geert
Andy Shevchenko March 5, 2024, 2:57 p.m. UTC | #3 
On Tue, Mar 05, 2024 at 09:23:07AM +0100, Geert Uytterhoeven wrote:
> On Tue, Mar 5, 2024 at 4:59 AM Chris Packham
> <chris.packham@alliedtelesis.co.nz> wrote:

...

> > +       priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
> > +       if (IS_ERR(priv->segment_gpios))
> > +               return PTR_ERR(priv->segment_gpios);
> 
> This needs some validation of priv->segment_gpios->ndescs, else the
> call to gpiod_set_array_value_cansleep() in seg_led_update() may
> trigger an out-of-bounds access of the values bitmap.

Alternatively we can call gpiod_count() beforehand and check its result.
Chris Packham March 5, 2024, 10:34 p.m. UTC | #4 
On 6/03/24 03:57, Andy Shevchenko wrote:
> On Tue, Mar 05, 2024 at 09:23:07AM +0100, Geert Uytterhoeven wrote:
>> On Tue, Mar 5, 2024 at 4:59 AM Chris Packham
>> <chris.packham@alliedtelesis.co.nz> wrote:
> ...
>
>>> +       priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
>>> +       if (IS_ERR(priv->segment_gpios))
>>> +               return PTR_ERR(priv->segment_gpios);
>> This needs some validation of priv->segment_gpios->ndescs, else the
>> call to gpiod_set_array_value_cansleep() in seg_led_update() may
>> trigger an out-of-bounds access of the values bitmap.
> Alternatively we can call gpiod_count() beforehand and check its result.
Unless there are any objections I think I'll go with the ndescs check as 
it'll be easier to update to the subnode style in the future. It does 
mean there will be some extra allocations/frees (handled via the devm_ 
APIs) in the error case.
Andy Shevchenko March 6, 2024, 10:58 a.m. UTC | #5 
On Wed, Mar 6, 2024 at 12:34 AM Chris Packham
<Chris.Packham@alliedtelesis.co.nz> wrote:
> On 6/03/24 03:57, Andy Shevchenko wrote:
> > On Tue, Mar 05, 2024 at 09:23:07AM +0100, Geert Uytterhoeven wrote:
> >> On Tue, Mar 5, 2024 at 4:59 AM Chris Packham
> >> <chris.packham@alliedtelesis.co.nz> wrote:

...

> >>> +       priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
> >>> +       if (IS_ERR(priv->segment_gpios))
> >>> +               return PTR_ERR(priv->segment_gpios);
> >> This needs some validation of priv->segment_gpios->ndescs, else the
> >> call to gpiod_set_array_value_cansleep() in seg_led_update() may
> >> trigger an out-of-bounds access of the values bitmap.
> > Alternatively we can call gpiod_count() beforehand and check its result.
> Unless there are any objections I think I'll go with the ndescs check as
> it'll be easier to update to the subnode style in the future.

Either works for me.

> It does
> mean there will be some extra allocations/frees (handled via the devm_
> APIs) in the error case.
diff mbox series

Patch

diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index d4be0a3695ce..898ecfb34ed7 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -211,6 +211,16 @@  config ARM_CHARLCD
 	  line and the Linux version on the second line, but that's
 	  still useful.
 
+config SEG_LED_GPIO
+	tristate "Generic 7-segment LED display"
+	select LINEDISP
+	help
+	  This driver supports a generic 7-segment LED display made up
+	  of GPIO pins connected to the individual segments.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called seg-led-gpio.
+
 menuconfig PARPORT_PANEL
 	tristate "Parallel port LCD/Keypad Panel support"
 	depends on PARPORT
diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
index a725010ca651..4a8ea41b0550 100644
--- a/drivers/auxdisplay/Makefile
+++ b/drivers/auxdisplay/Makefile
@@ -15,3 +15,4 @@  obj-$(CONFIG_PARPORT_PANEL)	+= panel.o
 obj-$(CONFIG_LCD2S)		+= lcd2s.o
 obj-$(CONFIG_LINEDISP)		+= line-display.o
 obj-$(CONFIG_MAX6959)		+= max6959.o
+obj-$(CONFIG_SEG_LED_GPIO)	+= seg-led-gpio.o
diff --git a/drivers/auxdisplay/seg-led-gpio.c b/drivers/auxdisplay/seg-led-gpio.c
new file mode 100644
index 000000000000..6c97c068f4c1
--- /dev/null
+++ b/drivers/auxdisplay/seg-led-gpio.c
@@ -0,0 +1,109 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for a 7-segment LED display
+ *
+ * The decimal point LED present on some devices is currently not
+ * supported.
+ *
+ * Copyright (C) Allied Telesis Labs
+ */
+
+#include <linux/bitmap.h>
+#include <linux/container_of.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/map_to_7segment.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include "line-display.h"
+
+struct seg_led_priv {
+	struct linedisp linedisp;
+	struct delayed_work work;
+	struct gpio_descs *segment_gpios;
+};
+
+static void seg_led_update(struct work_struct *work)
+{
+	struct seg_led_priv *priv = container_of(work, struct seg_led_priv, work.work);
+	struct linedisp *linedisp = &priv->linedisp;
+	struct linedisp_map *map = linedisp->map;
+	DECLARE_BITMAP(values, 8) = { 0 };
+
+	bitmap_set_value8(values, map_to_seg7(&map->map.seg7, linedisp->buf[0]), 0);
+
+	gpiod_set_array_value_cansleep(priv->segment_gpios->ndescs, priv->segment_gpios->desc,
+				       priv->segment_gpios->info, values);
+}
+
+static int seg_led_linedisp_get_map_type(struct linedisp *linedisp)
+{
+	struct seg_led_priv *priv = container_of(linedisp, struct seg_led_priv, linedisp);
+
+	INIT_DELAYED_WORK(&priv->work, seg_led_update);
+	return LINEDISP_MAP_SEG7;
+}
+
+static void seg_led_linedisp_update(struct linedisp *linedisp)
+{
+	struct seg_led_priv *priv = container_of(linedisp, struct seg_led_priv, linedisp);
+
+	schedule_delayed_work(&priv->work, 0);
+}
+
+static const struct linedisp_ops seg_led_linedisp_ops = {
+	.get_map_type = seg_led_linedisp_get_map_type,
+	.update = seg_led_linedisp_update,
+};
+
+static int seg_led_probe(struct platform_device *pdev)
+{
+	struct seg_led_priv *priv;
+	struct device *dev = &pdev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, priv);
+
+	priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->segment_gpios))
+		return PTR_ERR(priv->segment_gpios);
+
+	return linedisp_register(&priv->linedisp, dev, 1, &seg_led_linedisp_ops);
+}
+
+static int seg_led_remove(struct platform_device *pdev)
+{
+	struct seg_led_priv *priv = platform_get_drvdata(pdev);
+
+	cancel_delayed_work_sync(&priv->work);
+	linedisp_unregister(&priv->linedisp);
+
+	return 0;
+}
+
+static const struct of_device_id seg_led_of_match[] = {
+	{ .compatible = "gpio-7-segment"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, seg_led_of_match);
+
+static struct platform_driver seg_led_driver = {
+	.probe = seg_led_probe,
+	.remove = seg_led_remove,
+	.driver = {
+		.name = "seg-led-gpio",
+		.of_match_table = seg_led_of_match,
+	},
+};
+module_platform_driver(seg_led_driver);
+
+MODULE_AUTHOR("Chris Packham <chris.packham@alliedtelesis.co.nz>");
+MODULE_DESCRIPTION("7 segment LED driver");
+MODULE_LICENSE("GPL");