Re: [RFC PATCH 3/3] drivers/mfd: rpisense: Raspberry Pi senseHAT 8x8 LED matrix display driver

[Peter Robinson]

On Sat, Aug 7, 2021 at 1:31 AM Joel Savitz <jsavitz@xxxxxxxxxx> wrote:
>
> This patch implements control of the 8x8 RGB LED matrix display.
>
> Signed-off-by: Charles Mirabile <cmirabil@xxxxxxxxxx>
> Signed-off-by: Mwesigwa Guma <mguma@xxxxxxxxxx>
> Signed-off-by: Joel Savitz <jsavitz@xxxxxxxxxx>
> ---
>  drivers/mfd/Makefile           |   1 +
>  drivers/mfd/rpisense-display.c | 242 +++++++++++++++++++++++++++++++++

I suspect this better fits in drivers/auxdisplay/

>  2 files changed, 243 insertions(+)
>  create mode 100644 drivers/mfd/rpisense-display.c
>
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 71356153ccdc..974518d9801b 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -265,6 +265,7 @@ obj-$(CONFIG_MFD_STMFX)     += stmfx.o
>  obj-$(CONFIG_MFD_KHADAS_MCU)   += khadas-mcu.o
>  obj-$(CONFIG_MFD_RPISENSE)     += rpisense-core.o
>  obj-$(CONFIG_MFD_RPISENSE)     += rpisense-js.o
> +obj-$(CONFIG_MFD_RPISENSE)     += rpisense-display.o
>  obj-$(CONFIG_MFD_ACER_A500_EC) += acer-ec-a500.o
>  obj-$(CONFIG_MFD_QCOM_PM8008)  += qcom-pm8008.o
>
> diff --git a/drivers/mfd/rpisense-display.c b/drivers/mfd/rpisense-display.c
> new file mode 100644
> index 000000000000..10a34fa0eece
> --- /dev/null
> +++ b/drivers/mfd/rpisense-display.c
> @@ -0,0 +1,242 @@
> +// 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/mfd/rpisense.h>
> +
> +#define GAMMA_SIZE sizeof_field(struct rpisense_display, gamma)
> +#define VMEM_SIZE sizeof_field(struct rpisense_display, vmem)
> +
> +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] = {
> +       [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,
> +       },
> +       [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 const struct file_operations rpisense_display_fops;
> +
> +static int rpisense_display_probe(struct platform_device *pdev)
> +{
> +       int ret;
> +
> +       struct rpisense *rpisense = dev_get_drvdata(&pdev->dev);
> +       struct rpisense_display *rpisense_display = &rpisense->display;
> +
> +       memcpy(rpisense_display->gamma, gamma_presets[lowlight], GAMMA_SIZE);
> +
> +       memset(rpisense_display->vmem, 0, VMEM_SIZE);
> +
> +       mutex_init(&rpisense_display->rw_mtx);
> +
> +       rpisense_display->mdev = (struct miscdevice) {
> +               .minor  = MISC_DYNAMIC_MINOR,
> +               .name   = "sense-hat",
> +               .mode   = 0666,
> +               .fops   = &rpisense_display_fops,
> +       };
> +
> +       ret = misc_register(&rpisense_display->mdev);
> +       if (ret < 0) {
> +               dev_err(&pdev->dev, "Could not register 8x8 LED matrix display.\n");
> +               return ret;
> +       }
> +
> +       dev_info(&pdev->dev, "8x8 LED matrix display registered with minor number %i",
> +               rpisense_display->mdev.minor);
> +
> +       rpisense_update_display(rpisense);
> +       return 0;
> +}
> +
> +static int rpisense_display_remove(struct platform_device *pdev)
> +{
> +       struct rpisense *rpisense = dev_get_drvdata(&pdev->dev);
> +       struct rpisense_display *rpisense_display = &rpisense->display;
> +
> +       misc_deregister(&rpisense_display->mdev);
> +       return 0;
> +}
> +
> +static loff_t rpisense_display_llseek(struct file *filp, loff_t pos, int whence)
> +{
> +       loff_t base;
> +
> +       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;
> +       }
> +       base += pos;
> +       if (base < 0 || base >= VMEM_SIZE)
> +               return -EINVAL;
> +       filp->f_pos = base;
> +       return base;
> +}
> +
> +static ssize_t
> +rpisense_display_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
> +{
> +       struct rpisense *rpisense = container_of(filp->private_data, struct rpisense, display.mdev);
> +       struct rpisense_display *rpisense_display = &rpisense->display;
> +       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(&rpisense_display->rw_mtx))
> +               return -ERESTARTSYS;
> +       if (copy_to_user(buf, rpisense_display->vmem + *f_pos, count))
> +               goto out;
> +       *f_pos += count;
> +       retval = count;
> +out:
> +       mutex_unlock(&rpisense_display->rw_mtx);
> +       return retval;
> +}
> +
> +static ssize_t
> +rpisense_display_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
> +{
> +       struct rpisense *rpisense = container_of(filp->private_data, struct rpisense, display.mdev);
> +       struct rpisense_display *rpisense_display = &rpisense->display;
> +       u8 temp[VMEM_SIZE];
> +
> +       if (*f_pos >= VMEM_SIZE)
> +               return -EFBIG;
> +       if (*f_pos + count > VMEM_SIZE)
> +               count = VMEM_SIZE - *f_pos;
> +       if (copy_from_user(temp, buf, count))
> +               return -EFAULT;
> +       if (mutex_lock_interruptible(&rpisense_display->rw_mtx))
> +               return -ERESTARTSYS;
> +       memcpy(rpisense_display->vmem + *f_pos, temp, count);
> +       rpisense_update_display(rpisense);
> +       *f_pos += count;
> +       mutex_unlock(&rpisense_display->rw_mtx);
> +       return count;
> +}
> +
> +static long rpisense_display_ioctl(struct file *filp, unsigned int cmd,
> +                            unsigned long arg)
> +{
> +       struct rpisense *rpisense = container_of(filp->private_data, struct rpisense, display.mdev);
> +       struct rpisense_display *rpisense_display = &rpisense->display;
> +       void __user *user_ptr = (void __user *)arg;
> +       u8 temp[GAMMA_SIZE];
> +       int ret;
> +
> +       if (mutex_lock_interruptible(&rpisense_display->rw_mtx))
> +               return -ERESTARTSYS;
> +       switch (cmd) {
> +       case SENSEDISP_IOGET_GAMMA:
> +               if (copy_to_user(user_ptr, rpisense_display->gamma, GAMMA_SIZE)) {
> +                       ret = -EFAULT;
> +                       goto out_unlock;
> +               }
> +               ret = 0;
> +               goto out_unlock;
> +       case SENSEDISP_IOSET_GAMMA:
> +               if (copy_from_user(temp, user_ptr, GAMMA_SIZE)) {
> +                       ret = -EFAULT;
> +                       goto out_unlock;
> +               }
> +               ret = 0;
> +               goto out_update;
> +       case SENSEDISP_IORESET_GAMMA:
> +               if (arg < GAMMA_DEFAULT || arg >= GAMMA_PRESET_COUNT) {
> +                       ret = -EINVAL;
> +                       goto out_unlock;
> +               }
> +               memcpy(temp, gamma_presets[arg], GAMMA_SIZE);
> +               ret = 0;
> +               goto out_update;
> +       default:
> +               ret = -EINVAL;
> +               goto out_unlock;
> +       }
> +out_update:
> +       memcpy(rpisense_display->gamma, temp, GAMMA_SIZE);
> +       rpisense_update_display(rpisense);
> +out_unlock:
> +       mutex_unlock(&rpisense_display->rw_mtx);
> +       return ret;
> +}
> +
> +static const struct file_operations rpisense_display_fops = {
> +       .owner          = THIS_MODULE,
> +       .llseek         = rpisense_display_llseek,
> +       .read           = rpisense_display_read,
> +       .write          = rpisense_display_write,
> +       .unlocked_ioctl = rpisense_display_ioctl,
> +};
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id rpisense_display_id[] = {
> +       { .compatible = "rpi,rpi-sense-fb" },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(of, rpisense_display_id);
> +#endif
> +
> +static struct platform_device_id rpisense_display_device_id[] = {
> +       { .name = "rpi-sense-fb" },

I don't think -fb is the best name for this device, it's not a
framebuffer display/driver.

> +       { },
> +};
> +MODULE_DEVICE_TABLE(platform, rpisense_display_device_id);
> +
> +static struct platform_driver rpisense_display_driver = {
> +       .probe = rpisense_display_probe,
> +       .remove = rpisense_display_remove,
> +       .driver = {
> +               .name = "rpi-sense-fb",
> +       },
> +};
> +
> +module_platform_driver(rpisense_display_driver);
> +
> +MODULE_DESCRIPTION("Raspberry Pi Sense HAT 8x8 LED matrix display driver");

Again include the original author in the cc:

> +MODULE_AUTHOR("Serge Schneider <serge@xxxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +
> --
> 2.27.0
>
>
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