[PATCH 3/6] drivers/auxdisplay: sensehat: Raspberry Pi Sense HAT display driver
Nicolas Saenz Julienne
nsaenzju at redhat.com
Tue Feb 8 04:36:58 PST 2022
On Wed, 2022-02-02 at 19:25 -0500, Charles Mirabile wrote:
> This patch adds the driver for the 8x8 RGB LED matrix display
> on the Sense HAT. It appears as a character device named sense-hat
> in /dev/. That special file is 192 bytes large and contains one byte
> for each color channel of each pixel. The overall layout is:
>
> col 1 col 8
> | |
> v v
> 0x00: R . . . R \
> 0x08: G . . . G |> row 1
> 0x10: B . . . B /
> . . .
> ... . . .
> . . .
> 0xA8: R . . . R \
> 0xB0: G . . . G |> row 8
> 0xB8: G . . . G /
>
> Each channel may have any value between 0 and 31 (larger values are
> wrapped) and are translated by a gamma table before being send to the
> device to provide a linear experience of brightness (the gamma table
> can be modified or reset using an ioctl call on the file). The constants
> for the ioctl are in the sensehat.h header also added in this patch.
>
> Co-developed-by: Mwesigwa Guma <mguma at redhat.com>
> Signed-off-by: Mwesigwa Guma <mguma at redhat.com>
> Co-developed-by: Joel Savitz <jsavitz at redhat.com>
> Signed-off-by: Joel Savitz <jsavitz at redhat.com>
> Co-developed-by: Daniel Bauman <dbauman at redhat.com>
> Signed-off-by: Daniel Bauman <dbauman at redhat.com>
> Signed-off-by: Charles Mirabile <cmirabil at redhat.com>
> ---
> drivers/auxdisplay/Kconfig | 8 +
> drivers/auxdisplay/Makefile | 1 +
> drivers/auxdisplay/sensehat-display.c | 264 ++++++++++++++++++++++++++
> include/uapi/linux/sensehat.h | 28 +++
> 4 files changed, 301 insertions(+)
> create mode 100644 drivers/auxdisplay/sensehat-display.c
> create mode 100644 include/uapi/linux/sensehat.h
>
> diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
> index 64012cda4d12..9bad1aade7a0 100644
> --- a/drivers/auxdisplay/Kconfig
> +++ b/drivers/auxdisplay/Kconfig
> @@ -203,6 +203,14 @@ config ARM_CHARLCD
> line and the Linux version on the second line, but that's
> still useful.
>
> +config SENSEHAT_DISPLAY
> + tristate "Raspberry Pi Sense HAT display driver"
> + depends on I2C
> + select MFD_SIMPLE_MFD_I2C
> + help
> + This is a driver for the Raspberry Pi Sensehat 8x8 RBG-LED matrix
> + you can access it as a misc device at /dev/sense-hat
> +
> menuconfig PARPORT_PANEL
> tristate "Parallel port LCD/Keypad Panel support"
> depends on PARPORT
> diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
> index 6968ed4d3f0a..30b2b7934046 100644
> --- a/drivers/auxdisplay/Makefile
> +++ b/drivers/auxdisplay/Makefile
> @@ -14,3 +14,4 @@ obj-$(CONFIG_HT16K33) += ht16k33.o
> obj-$(CONFIG_PARPORT_PANEL) += panel.o
> obj-$(CONFIG_LCD2S) += lcd2s.o
> obj-$(CONFIG_LINEDISP) += line-display.o
> +obj-$(CONFIG_SENSEHAT_DISPLAY) += sensehat-display.o
> diff --git a/drivers/auxdisplay/sensehat-display.c b/drivers/auxdisplay/sensehat-display.c
> new file mode 100644
> index 000000000000..08b397a544f0
> --- /dev/null
> +++ b/drivers/auxdisplay/sensehat-display.c
> @@ -0,0 +1,264 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Raspberry Pi Sense HAT 8x8 LED matrix display driver
> + * http://raspberrypi.org
> + *
> + * Copyright (C) 2015 Raspberry Pi
> + * Copyright (C) 2021 Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + *
> + * Original Author: Serge Schneider
> + * Revised for upstream Linux by: Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/miscdevice.h>
> +#include <linux/regmap.h>
> +#include <linux/property.h>
> +#include <linux/sensehat.h>
> +
> +#define GAMMA_SIZE 32
> +#define VMEM_SIZE 192
> +
> +struct sensehat_display {
> + struct platform_device *pdev;
> + struct miscdevice mdev;
> + struct mutex rw_mtx;
> + u8 gamma[GAMMA_SIZE];
> + u8 vmem[VMEM_SIZE];
> + u32 display_register;
> +};
> +
> +static bool lowlight;
> +module_param(lowlight, bool, 0);
> +MODULE_PARM_DESC(lowlight, "Reduce LED matrix brightness to one third");
> +
> +static const u8 gamma_presets[][GAMMA_SIZE] = {
> + [SENSEHAT_GAMMA_DEFAULT] = {
> + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01,
> + 0x02, 0x02, 0x03, 0x03, 0x04, 0x05, 0x06, 0x07,
> + 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0E, 0x0F, 0x11,
> + 0x12, 0x14, 0x15, 0x17, 0x19, 0x1B, 0x1D, 0x1F,
> + },
> + [SENSEHAT_GAMMA_LOWLIGHT] = {
> + 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
> + 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02,
> + 0x03, 0x03, 0x03, 0x04, 0x04, 0x05, 0x05, 0x06,
> + 0x06, 0x07, 0x07, 0x08, 0x08, 0x09, 0x0A, 0x0A,
> + },
> +};
> +
> +static void sensehat_update_display(struct sensehat_display *display)
> +{
> + int i, ret;
> + struct regmap *regmap = dev_get_regmap(display->pdev->dev.parent, NULL);
Same comment as with joystick.
> + u8 temp[VMEM_SIZE];
> +
> + for (i = 0; i < VMEM_SIZE; ++i)
> + temp[i] = display->gamma[display->vmem[i] & 0x1f];
> +
> + ret = regmap_bulk_write(regmap, display->display_register, temp,
> + VMEM_SIZE);
> + if (ret < 0)
> + dev_err(&display->pdev->dev,
> + "Update to 8x8 LED matrix display failed");
> +}
> +
> +static loff_t sensehat_display_llseek(struct file *filp, loff_t offset,
> + int whence)
> +{
> + loff_t base, pos;
> +
> + switch (whence) {
> + case SEEK_SET:
> + base = 0;
> + break;
> + case SEEK_CUR:
> + base = filp->f_pos;
> + break;
> + case SEEK_END:
> + base = VMEM_SIZE;
> + break;
> + default:
> + return -EINVAL;
> + }
> + pos = base + offset;
> + if (pos < 0 || pos >= VMEM_SIZE)
> + return -EINVAL;
> + filp->f_pos = pos;
> + return base;
> +}
> +
> +static ssize_t sensehat_display_read(struct file *filp, char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct sensehat_display *sensehat_display =
> + container_of(filp->private_data, struct sensehat_display, mdev);
> + ssize_t retval = -EFAULT;
> +
> + if (*f_pos >= VMEM_SIZE)
> + return 0;
> + if (*f_pos + count > VMEM_SIZE)
> + count = VMEM_SIZE - *f_pos;
> + if (mutex_lock_interruptible(&sensehat_display->rw_mtx))
> + return -ERESTARTSYS;
> + if (copy_to_user(buf, sensehat_display->vmem + *f_pos, count))
> + goto out;
> + *f_pos += count;
> + retval = count;
> +out:
> + mutex_unlock(&sensehat_display->rw_mtx);
> + return retval;
> +}
> +
> +static ssize_t sensehat_display_write(struct file *filp, const char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct sensehat_display *sensehat_display =
> + container_of(filp->private_data, struct sensehat_display, mdev);
> + int ret = count;
> +
> + if (*f_pos >= VMEM_SIZE)
> + return -EFBIG;
> + if (*f_pos + count > VMEM_SIZE)
> + count = VMEM_SIZE - *f_pos;
> + if (mutex_lock_interruptible(&sensehat_display->rw_mtx))
> + return -ERESTARTSYS;
> + if (copy_from_user(sensehat_display->vmem + *f_pos, buf, count)) {
> + ret = -EFAULT;
> + goto out;
> + }
> + sensehat_update_display(sensehat_display);
> + *f_pos += count;
> +out:
> + mutex_unlock(&sensehat_display->rw_mtx);
> + return ret;
> +}
> +
> +static long sensehat_display_ioctl(struct file *filp, unsigned int cmd,
> + unsigned long arg)
> +{
> + struct sensehat_display *sensehat_display =
> + container_of(filp->private_data, struct sensehat_display, mdev);
> + void __user *user_ptr = (void __user *)arg;
> + int i, ret = 0;
> +
> + if (mutex_lock_interruptible(&sensehat_display->rw_mtx))
> + return -ERESTARTSYS;
nit: add space, here and after the switch statement.
> + switch (cmd) {
> + case SENSEDISP_IOGET_GAMMA:
> + if (copy_to_user(user_ptr, sensehat_display->gamma, GAMMA_SIZE))
> + ret = -EFAULT;
> + goto no_update;
> + case SENSEDISP_IOSET_GAMMA:
> + if (copy_from_user(sensehat_display->gamma, user_ptr,
> + GAMMA_SIZE))
> + ret = -EFAULT;
> + break;
> + case SENSEDISP_IORESET_GAMMA:
> + if (arg >= SENSEHAT_GAMMA_PRESET_COUNT) {
> + ret = -EINVAL;
> + goto no_update;
> + }
> + memcpy(sensehat_display->gamma, gamma_presets[arg], GAMMA_SIZE);
> + goto no_check;
> + default:
> + ret = -EINVAL;
> + break;
> + }
> + for (i = 0; i < GAMMA_SIZE; ++i)
> + sensehat_display->gamma[i] &= 0x1f;
> +no_check:
> + sensehat_update_display(sensehat_display);
> +no_update:
> + mutex_unlock(&sensehat_display->rw_mtx);
> + return ret;
> +}
> +
> +static const struct file_operations sensehat_display_fops = {
> + .owner = THIS_MODULE,
> + .llseek = sensehat_display_llseek,
> + .read = sensehat_display_read,
> + .write = sensehat_display_write,
> + .unlocked_ioctl = sensehat_display_ioctl,
> +};
> +
> +static int sensehat_display_probe(struct platform_device *pdev)
> +{
> + int ret;
> +
> + struct sensehat_display *sensehat_display =
> + devm_kzalloc(&pdev->dev, sizeof(*sensehat_display), GFP_KERNEL);
> +
> + sensehat_display->pdev = pdev;
> +
> + memcpy(sensehat_display->gamma, gamma_presets[lowlight], GAMMA_SIZE);
> +
> + memset(sensehat_display->vmem, 0, VMEM_SIZE);
You don't nee this, kzalloc already zeroes the memory.
> +
> + mutex_init(&sensehat_display->rw_mtx);
> +
> + ret = device_property_read_u32(&pdev->dev, "reg",
> + &sensehat_display->display_register);
Same comment as with joystick.
> + if (ret) {
> + dev_err(&pdev->dev, "Could not read register property.\n");
> + return ret;
> + }
> +
> + sensehat_display->mdev = (struct miscdevice){
> + .minor = MISC_DYNAMIC_MINOR,
> + .name = "sense-hat",
> + .mode = 0666,
> + .fops = &sensehat_display_fops,
> + };
> +
> + ret = misc_register(&sensehat_display->mdev);
> + if (ret < 0) {
> + dev_err(&pdev->dev,
> + "Could not register 8x8 LED matrix display.\n");
> + return ret;
> + }
> +
> + ret = devm_add_action(&pdev->dev, (void *)misc_deregister,
> + &sensehat_display->mdev);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Could not add misc device to devm\n");
> + return ret;
> + }
Instead of doing this I'd add a .remove callback to the platform driver.
> +
> + dev_info(&pdev->dev,
> + "8x8 LED matrix display registered with minor number %i",
> + sensehat_display->mdev.minor);
> +
> + sensehat_update_display(sensehat_display);
This could potentially race with an app accessing the misc device?
> + return 0;
> +}
> +
> +static const struct of_device_id sensehat_display_device_id[] = {
> + { .compatible = "raspberrypi,sensehat-display" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, sensehat_display_device_id);
> +
> +static struct platform_driver sensehat_display_driver = {
> + .probe = sensehat_display_probe,
> + .driver = {
> + .name = "sensehat-display",
> + .of_match_table = sensehat_display_device_id,
> + },
> +};
> +
> +module_platform_driver(sensehat_display_driver);
> +
> +MODULE_DESCRIPTION("Raspberry Pi Sense HAT 8x8 LED matrix display driver");
> +MODULE_AUTHOR("Serge Schneider <serge at raspberrypi.org>");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/sensehat.h b/include/uapi/linux/sensehat.h
> new file mode 100644
> index 000000000000..cae07568a5eb
> --- /dev/null
> +++ b/include/uapi/linux/sensehat.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later WITH Linux-syscall-note */
> +/*
> + * Raspberry Pi Sense HAT core driver
> + * http://raspberrypi.org
> + *
> + * Copyright (C) 2015 Raspberry Pi
> + * Copyright (C) 2021 Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + *
> + * Original Author: Serge Schneider
> + * Revised for upstream Linux by: Charles Mirabile, Mwesigwa Guma, Joel Savitz
> + */
> +
> +#ifndef _UAPILINUX_SENSEHAT_H_
> +#define _UAPILINUX_SENSEHAT_H_
> +
> +#define SENSEDISP_IOC_MAGIC 0xF1
> +
> +#define SENSEDISP_IOGET_GAMMA _IO(SENSEDISP_IOC_MAGIC, 0)
> +#define SENSEDISP_IOSET_GAMMA _IO(SENSEDISP_IOC_MAGIC, 1)
> +#define SENSEDISP_IORESET_GAMMA _IO(SENSEDISP_IOC_MAGIC, 2)
> +
> +enum gamma_preset {
> + SENSEHAT_GAMMA_DEFAULT = 0,
> + SENSEHAT_GAMMA_LOWLIGHT,
> + SENSEHAT_GAMMA_PRESET_COUNT,
> +};
> +
> +#endif
--
Nicolás Sáenz
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