[PATCH] DRIVER: request_firmware() hotplug interface documentation

Documentation/firmware_class/README

+
+ request_firmware() hotplug interface:
+ ------------------------------------
+	Copyright (C) 2003 Manuel Estrada Sainz <ranty@debian.org>
+
+ Why:
+ ---
+
+ Today, the most extended way to use firmware in the Linux kernel is linking
+ it statically in a header file. Which has political and technical issues:
+
+  1) Some firmware is not legal to redistribute.
+  2) The firmware occupies memory permanently, even though it often is just
+     used once.
+  3) Some people, like the Debian crowd, don't consider some firmware free
+     enough and remove entire drivers (e.g.: keyspan).
+
+ about in-kernel persistence:
+ ---------------------------
+ Under some circumstances, as explained below, it would be interesting to keep
+ firmware images in non-swappable kernel memory or even in the kernel image
+ (probably within initramfs).
+
+ Note that this functionality has not been implemented.
+
+ - Why OPTIONAL in-kernel persistence may be a good idea sometimes:
+ 
+	- If the device that needs the firmware is needed to access the
+	  filesystem. When upon some error the device has to be reset and the
+	  firmware reloaded, it won't be possible to get it from userspace.
+	  e.g.:
+		- A diskless client with a network card that needs firmware.
+		- The filesystem is stored in a disk behind an scsi device
+		  that needs firmware.
+	- Replacing buggy DSDT/SSDT ACPI tables on boot.
+	  Note: this would require the persistent objects to be included
+	  within the kernel image, probably within initramfs.
+	  
+   And the same device can be needed to access the filesystem or not depending
+   on the setup, so I think that the choice on what firmware to make
+   persistent should be left to userspace.
+
+ - Why register_firmware()+__init can be useful:
+ 	- For boot devices needing firmware.
+	- To make the transition easier:
+		The firmware can be declared __init and register_firmware()
+		called on module_init. Then the firmware is warranted to be
+		there even if "firmware hotplug userspace" is not there yet or
+		it doesn't yet provide the needed firmware.
+		Once the firmware is widely available in userspace, it can be
+		removed from the kernel. Or made optional (CONFIG_.*_FIRMWARE).
+
+	In either case, if firmware hotplug support is there, it can move the
+	firmware out of kernel memory into the real filesystem for later
+	usage.
+
+	Note: If persistence is implemented on top of initramfs,
+	register_firmware() may not be appropriate.

Documentation/firmware_class/firmware_sample_driver.c

+/*
+ * firmware_sample_driver.c -
+ *
+ * Copyright (c) 2003 Manuel Estrada Sainz <ranty@debian.org>
+ *
+ * Sample code on how to use request_firmware() from drivers.
+ *
+ * Note that register_firmware() is currently useless.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/device.h>
+
+#include "linux/firmware.h"
+
+#define WE_CAN_NEED_FIRMWARE_BEFORE_USERSPACE_IS_AVAILABLE
+#ifdef WE_CAN_NEED_FIRMWARE_BEFORE_USERSPACE_IS_AVAILABLE
+char __init inkernel_firmware[] = "let's say that this is firmware\n";
+#endif
+
+static struct device ghost_device = {
+	.name      = "Ghost Device",
+	.bus_id    = "ghost0",
+};
+
+
+static void sample_firmware_load(char *firmware, int size)
+{
+	u8 buf[size+1];
+	memcpy(buf, firmware, size);
+	buf[size] = '\0';
+	printk("firmware_sample_driver: firmware: %s\n", buf);
+}
+
+static void sample_probe_default(void)
+{
+	/* uses the default method to get the firmware */
+        const struct firmware *fw_entry;
+	printk("firmware_sample_driver: a ghost device got inserted :)\n");
+
+        if(request_firmware(&fw_entry, "sample_driver_fw", &ghost_device)!=0)
+	{
+		printk(KERN_ERR
+		       "firmware_sample_driver: Firmware not available\n");
+		return;
+	}
+	
+	sample_firmware_load(fw_entry->data, fw_entry->size);
+
+	release_firmware(fw_entry);
+
+	/* finish setting up the device */
+}
+static void sample_probe_specific(void)
+{
+	/* Uses some specific hotplug support to get the firmware from
+	 * userspace  directly into the hardware, or via some sysfs file */
+
+	/* NOTE: This currently doesn't work */
+
+	printk("firmware_sample_driver: a ghost device got inserted :)\n");
+
+        if(request_firmware(NULL, "sample_driver_fw", &ghost_device)!=0)
+	{
+		printk(KERN_ERR
+		       "firmware_sample_driver: Firmware load failed\n");
+		return;
+	}
+	
+	/* request_firmware blocks until userspace finished, so at
+	 * this point the firmware should be already in the device */
+
+	/* finish setting up the device */
+}
+static void sample_probe_async_cont(const struct firmware *fw, void *context)
+{
+	if(!fw){
+		printk(KERN_ERR
+		       "firmware_sample_driver: firmware load failed\n");
+		return;
+	}
+
+	printk("firmware_sample_driver: device pointer \"%s\"\n",
+	       (char *)context);
+	sample_firmware_load(fw->data, fw->size);
+}
+static void sample_probe_async(void)
+{
+	/* Let's say that I can't sleep */
+	int error;
+	error = request_firmware_nowait (THIS_MODULE,
+					 "sample_driver_fw", &ghost_device,
+					 "my device pointer",
+					 sample_probe_async_cont);
+	if(error){
+		printk(KERN_ERR 
+		       "firmware_sample_driver:"
+		       " request_firmware_nowait failed\n");
+	}
+}
+
+static int sample_init(void)
+{
+#ifdef WE_CAN_NEED_FIRMWARE_BEFORE_USERSPACE_IS_AVAILABLE
+	register_firmware("sample_driver_fw", inkernel_firmware,
+			  sizeof(inkernel_firmware));
+#endif
+	device_initialize(&ghost_device);
+	/* since there is no real hardware insertion I just call the
+	 * sample probe functions here */
+	sample_probe_specific();
+	sample_probe_default();
+	sample_probe_async();
+	return 0;
+}
+static void __exit sample_exit(void)
+{
+}
+
+module_init (sample_init);
+module_exit (sample_exit);
+
+MODULE_LICENSE("GPL");

Documentation/firmware_class/firmware_sample_firmware_class.c

+/*
+ * firmware_sample_firmware_class.c -
+ *
+ * Copyright (c) 2003 Manuel Estrada Sainz <ranty@debian.org>
+ *
+ * NOTE: This is just a probe of concept, if you think that your driver would
+ * be well served by this mechanism please contact me first.
+ *
+ * DON'T USE THIS CODE AS IS
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/timer.h>
+#include <asm/hardirq.h>
+
+#include "linux/firmware.h"
+
+MODULE_AUTHOR("Manuel Estrada Sainz <ranty@debian.org>");
+MODULE_DESCRIPTION("Hackish sample for using firmware class directly");
+MODULE_LICENSE("GPL");
+
+static inline struct class_device *to_class_dev(struct kobject *obj)
+{
+	return container_of(obj,struct class_device,kobj);
+}
+static inline
+struct class_device_attribute *to_class_dev_attr(struct attribute *_attr)
+{
+	return container_of(_attr,struct class_device_attribute,attr);
+}
+
+int sysfs_create_bin_file(struct kobject * kobj, struct bin_attribute * attr);
+int sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr);
+
+struct firmware_priv {
+	char fw_id[FIRMWARE_NAME_MAX];
+	s32 loading:2;
+	u32 abort:1;
+};
+
+extern struct class firmware_class;
+
+static ssize_t firmware_loading_show(struct class_device *class_dev, char *buf)
+{
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+	return sprintf(buf, "%d\n", fw_priv->loading);
+}
+static ssize_t firmware_loading_store(struct class_device *class_dev,
+				      const char *buf, size_t count)
+{
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+	int prev_loading = fw_priv->loading;
+
+	fw_priv->loading = simple_strtol(buf, NULL, 10);
+	
+	switch(fw_priv->loading){
+	case -1:
+		/* abort load an panic */
+		break;
+	case 1:
+		/* setup load */
+		break;
+	case 0:
+		if(prev_loading==1){
+			/* finish load and get the device back to working
+			 * state */
+		}
+		break;
+	}
+
+	return count;
+}
+static CLASS_DEVICE_ATTR(loading, 0644,
+			 firmware_loading_show, firmware_loading_store);
+
+static ssize_t firmware_data_read(struct kobject *kobj,
+				  char *buffer, loff_t offset, size_t count)
+{
+	struct class_device *class_dev = to_class_dev(kobj);
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+
+	/* read from the devices firmware memory */
+
+	return count;
+}
+static ssize_t firmware_data_write(struct kobject *kobj,
+				   char *buffer, loff_t offset, size_t count)
+{
+	struct class_device *class_dev = to_class_dev(kobj);
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+
+	/* write to the devices firmware memory */
+
+	return count;
+}
+static struct bin_attribute firmware_attr_data = {
+	.attr = {.name = "data", .mode = 0644},
+	.size = 0,
+	.read = firmware_data_read,
+	.write = firmware_data_write,
+};
+static int fw_setup_class_device(struct class_device *class_dev,
+				 const char *fw_name,
+				 struct device *device)
+{
+	int retval = 0;
+	struct firmware_priv *fw_priv = kmalloc(sizeof(struct firmware_priv),
+						GFP_KERNEL);
+
+	if(!fw_priv){
+		retval = -ENOMEM;
+		goto out;
+	}
+	memset(fw_priv, 0, sizeof(*fw_priv));
+	memset(class_dev, 0, sizeof(*class_dev));
+
+	strncpy(fw_priv->fw_id, fw_name, FIRMWARE_NAME_MAX);
+	fw_priv->fw_id[FIRMWARE_NAME_MAX-1] = '\0';
+
+	strncpy(class_dev->class_id, device->bus_id, BUS_ID_SIZE);
+	class_dev->class_id[BUS_ID_SIZE-1] = '\0';
+	class_dev->dev = device;
+
+	class_dev->class = &firmware_class,
+	class_set_devdata(class_dev, fw_priv);
+	retval = class_device_register(class_dev);
+	if (retval){
+		printk(KERN_ERR "%s: class_device_register failed\n",
+		       __FUNCTION__);
+		goto error_free_fw_priv;
+	}
+
+	retval = sysfs_create_bin_file(&class_dev->kobj, &firmware_attr_data);
+	if (retval){
+		printk(KERN_ERR "%s: sysfs_create_bin_file failed\n",
+		       __FUNCTION__);
+		goto error_unreg_class_dev;
+	}
+
+	retval = class_device_create_file(class_dev,
+					  &class_device_attr_loading);
+	if (retval){
+		printk(KERN_ERR "%s: class_device_create_file failed\n",
+		       __FUNCTION__);
+		goto error_remove_data;
+	}
+
+	goto out;
+	
+error_remove_data:
+	sysfs_remove_bin_file(&class_dev->kobj, &firmware_attr_data);
+error_unreg_class_dev:
+	class_device_unregister(class_dev);
+error_free_fw_priv:
+	kfree(fw_priv);
+out:
+	return retval;
+}
+static void fw_remove_class_device(struct class_device *class_dev)
+{
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+
+	class_device_remove_file(class_dev, &class_device_attr_loading);
+	sysfs_remove_bin_file(&class_dev->kobj, &firmware_attr_data);
+	class_device_unregister(class_dev);
+}
+
+static struct class_device *class_dev;
+
+static struct device my_device = {
+	.name      = "Sample Device",
+	.bus_id    = "my_dev0",
+};
+
+static int __init firmware_sample_init(void)
+{
+	int error;
+
+	device_initialize(&my_device);
+	class_dev = kmalloc(sizeof(struct class_device), GFP_KERNEL);
+	if(!class_dev)
+		return -ENOMEM;
+
+	error = fw_setup_class_device(class_dev, "my_firmware_image",
+				      &my_device);
+	if(error){
+		kfree(class_dev);
+		return error;
+	}
+        return 0;
+
+}
+static void __exit firmware_sample_exit(void)
+{
+	struct firmware_priv *fw_priv = class_get_devdata(class_dev);
+	fw_remove_class_device(class_dev);
+	kfree(fw_priv);
+	kfree(class_dev);
+}
+module_init(firmware_sample_init);
+module_exit(firmware_sample_exit);
+

Documentation/firmware_class/hotplug-script

+#!/bin/sh
+
+# Simple hotplug script sample:
+# 
+# Both $DEVPATH and $FIRMWARE are already provided in the environment.
+
+HOTPLUG_FW_DIR=/usr/lib/hotplug/firmware/
+
+echo 1 > /sysfs/$DEVPATH/loading
+cat $HOTPLUG_FW_DIR/$FIRMWARE > /sysfs/$DEVPATH/data
+echo 0 > /sysfs/$DEVPATH/loading
+
+# To cancel the load in case of error:
+#
+#	echo -1 > /sysfs/$DEVPATH/loading
+#