Re: [RFC] What are the goals for the architecture of an in-kernel IR system?

Mauro Carvalho Chehab
2010-03-28T23:23:35Z

Dmitry Torokhov wrote:
> On Fri, Mar 26, 2010 at 11:40:41AM -0300, Mauro Carvalho Chehab wrote:
>> David Härdeman wrote:
>>> On Thu, Mar 25, 2010 at 11:42:33AM -0300, Mauro Carvalho Chehab wrote:
>>>>> 10) extend keycode table replacement to support big/variable
>>>>> sized scancodes;
>>>> Pending.
>>>>
>>>> The current limit here is the scancode ioctl's are defined as:
>>>>
>>>> #define EVIOCGKEYCODE _IOR('E', 0x04, int[2]) /* get keycode */
>>>> #define EVIOCSKEYCODE _IOW('E', 0x04, int[2]) /* set keycode */
>>>>
>>>> As int size is 32 bits, and we must pass both 64 (or even bigger) scancodes, associated
>>>> with a keycode, there's not enough bits there for IR.
>>>>
>>>> The better approach seems to create an struct with an arbitrary long size, like:
>>>>
>>>> struct keycode_table_entry {
>>>> unsigned keycode;
>>>> char scancode[32]; /* 32 is just an arbitrary long array - maybe shorter */
>>>> int len;
>>>> }
>>>>
>>>> and re-define the ioctls. For example we might be doing:
>>>>
>>>> #define EVIOCGKEYCODEBIG _IOR('E', 0x04, struct keycode_table_entry)
>>>> #define EVIOCSKEYCODEBIG _IOW('E', 0x04, struct keycode_table_entry)
>>>> #define EVIOCLEARKEYCODEBIG _IOR('E', 0x04, void)
>>>>
>>>> Provided that the size for struct keycode_table_entry is different, _IO will generate
>>>> a different magic number for those.
>>>>
>>>> Or, instead of using 0x04, just use another sequential number at the 'E' namespace.
>>>>
>>>> An specific function to clear the table is needed with big scancode space,
>>>> as already discussed.
>>>>
>>> I'd suggest:
>>>
>>> struct keycode_table_entry {
>>> unsigned keycode;
>>> unsigned index;
>>> unsigned len;
>>> char scancode[];
>>> };
>>>
>>> Use index in EVIOCGKEYCODEBIG to look up a keycode (all other fields are
>>> ignored), that way no special function to clear the table is necessary,
>>> instead you do a loop with:
>>>
>>> EVIOCGKEYCODEBIG (with index 0)
>>> EVIOCSKEYCODEBIG (with the returned struct from EVIOCGKEYCODEBIG and
>>> keycode = KEY_RESERVED)
>>>
>>> until EVIOCGKEYCODEBIG returns an error.
>> Makes sense.
>
> Yes, I think so too. Just need a nice way to handle transition, I'd
> like in the end to have drivers implement only the improved methods and
> map legacy methods in evdev.

See the attached RFC barely tested patch.

On this patch, I'm using the following definitions for the ioctl:

struct keycode_table_entry {
__u32 keycode; /* e.g. KEY_A */
__u32 index; /* Index for the given scan/key table */
__u32 len; /* Lenght of the scancode */
__u32 reserved[2]; /* Reserved for future usage */
char *scancode; /* scancode, in machine-endian */
};

#define EVIOCGKEYCODEBIG _IOR('E', 0x04, struct keycode_table_entry) /* get keycode */
#define EVIOCSKEYCODEBIG _IOW('E', 0x04, struct keycode_table_entry) /* set keycode */

I tried to do the compat backport on a nice way, on both directions, e. g.:

1) an userspace app using EVIO[CS]GKEYCODEBIG to work with a legacy driver.
2) a driver implementing the new methods to accept the legacy EVIO[CS]GKEYCODE;

For the test of (1), I implemented the following clear keytable code:

struct keycode_table_entry kt;
uint32_t scancode, i;

memset(&kt, 0, sizeof(kt));
kt.len = sizeof(scancode);
kt.scancode = (char *)&scancode;

for (i = 0; rc == 0; i++) {
kt.index = i;
kt.keycode = KEY_RESERVED;
rc = ioctl(fd, EVIOCSKEYCODEBIG, &kt);
}
fprintf(stderr, "Cleaned %i keycode(s)\n", i - 1);

It worked properly. I didn't test (2) yet.

The read keytable would also be trivial. However, there are some troubles when
implementing the code to add/replace a value at the table, in a way that it
would allow the legacy drivers to work:

- With a real CODEBIG support, the index number will be different than the
scancode number. So, let's say that this is the driver table:

index scancode keycode
------------------------
0 0x1e00 KEY_0
1 0x1e01 KEY_1
2 0x1e02 KEY_2
3 0x1e03 KEY_3
4 0x1e04 KEY_4
5 0x1e05 KEY_5
6 0x1e06 KEY_6
7 0x1e07 KEY_7
8 0x1e08 KEY_8
9 0x1e09 KEY_9

Let's suppose that the user wants to overwrite the entry 5, attributing a new scancode/keycode
to entry 5 (for example, associating 0x1e0a with KEY-A).

A valid EVIOCSKEYCODEBIG call to change this code would be:

kt->index = 5;
*(uint32_t *)kt->scancode = 0x1e0a;
*(uint32_t *)kt->keycode = KEY_A;
rc = ioctl(fd, EVIOCSKEYCODEBIG, &kt);

With EVIOCSKEYCODE, this requires two separate operations:

int codes[2];
code[0] = 0x1e05;
code[1] = KEY_RESERVED;
rc = ioctl(fd, EVIOCSKEYCODE, &codes];

code[0] = 0x1e0a;
code[1] = KEY_A;
rc = ioctl(fd, EVIOCSKEYCODE, &codes];

In the case of EVIOCSKEYCODEBIG call, the driver will need to:

1) Check If the scancode is not being used yet on any entry different than index=5.
If it is in use, it should return an error.
If not, replace the scancode/keycode.

2) Check if index is equal to the length of the array + 1. If so, create a new entry.

3) check if the index is bigger than length + 1 and return an error, if so.

For the EVIOSKEYCODE emulation by an EVIOCSKEYCODEBIG driver, index=5 won't work.
The driver will need to use the scancode. However, if we do this way, the
cleanup logic will break, as scancode is equal to zero.

So, I think that having an index here is not a good idea: it will just create some
implementation troubles. We can archive the same result without the index, and having
a fast clean_table code by just reading the used scancodes and associating them
with KEY_RESERVED.

So, I'll be working on another patch with this different implementation.

I also noticed another problem: kernel should have some way to report the expected
size of the scancode to userspace, especially if we want to have the compatibility
code (since, with compat, a scancode maximum size need to be 32 bits, otherwise
the code won't work).

I'll likely adding another control that returns the size of the scancode.

Comments?

Cheers,
Mauro

---

This is the RFC patch I wrote here for my tests.

commit 6bf412eedaa05f28d5ce50795d3ac64ec41c3031
Author: Mauro Carvalho Chehab <mchehab@redhat.com>
Date: Sun Mar 28 04:02:36 2010 -0300

input: Add support for EVIO[CS]GKEYCODEBIG

Several devices use a high number of bits for scancodes. One important
group is the Remote Controllers. Some new protocols like RC-6 define a
scancode space of 64 bits.

The current EVIO[CS]GKEYCODE ioctls allow replace the scancode/keycode
translation tables, but it is limited to up to 32 bits for scancode.

Also, if userspace wants to clean the existing table, replacing it by
a new one, it needs to run a loop calling the old ioctls, over the
entire sparsed scancode userspace.

To solve those problems, this patch introduces two new ioctls:
EVIOCGKEYCODEBIG - reads a scancode from the translation table;
EVIOSGKEYCODEBIG - writes a scancode into the translation table.

The EVIOSGKEYCODEBIG can also be used to cleanup the translation entries
by associating KEY_RESERVED to a scancode.

By default, kernel will implement a default handler that will work with
both EVIO[CS]GKEYCODEBIG and the legacy EVIO[CS]GKEYCODE ioctls.

Compatibility code were also added to allow drivers that implement
only the ops handler for EVIO[CS]GKEYCODE to keep working.

Userspace compatibility for EVIO[CS]GKEYCODE is also granted: the evdev/input
ioctl handler will automatically map those ioctls with the new
getkeycodebig()/setkeycodebig() operations to handle a request using the
legacy API.

So, new drivers should only implement the EVIO[CS]GKEYCODEBIG operation
handlers: getkeycodebig()/setkeycodebig().

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 258c639..aed5acc 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -513,6 +513,7 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
struct input_absinfo abs;
struct ff_effect effect;
int __user *ip = (int __user *)p;
+ struct keycode_table_entry __user *kt = p;
int i, t, u, v;
int error;

@@ -567,6 +568,25 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,

return input_set_keycode(dev, t, v);

+ case EVIOCGKEYCODEBIG:
+ if (copy_from_user(kt, &dev->id, _IOC_SIZE(cmd)))
+ return -EFAULT;
+
+ error = input_get_keycode_big(dev, kt);
+ if (error)
+ return error;
+
+ if (copy_to_user(kt, &dev->id, _IOC_SIZE(cmd)))
+ return -EFAULT;
+
+ return 0;
+
+ case EVIOCSKEYCODEBIG:
+ if (copy_from_user(p, &dev->id, _IOC_SIZE(cmd)))
+ return -EFAULT;
+
+ return input_set_keycode_big(dev, kt);
+
case EVIOCRMFF:
return input_ff_erase(dev, (int)(unsigned long) p, file);

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 86cb2d2..0437c75 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -551,6 +551,11 @@ static void input_disconnect_device(struct input_dev *dev)
spin_unlock_irq(&dev->event_lock);
}

+/*
+ * Those routines handle the default case where no [gs]etkeycode() is
+ * defined. In this case, an array indexed by the scancode is used.
+ */
+
static int input_fetch_keycode(struct input_dev *dev, int scancode)
{
switch (dev->keycodesize) {
@@ -566,57 +571,88 @@ static int input_fetch_keycode(struct input_dev *dev, int scancode)
}

static int input_default_getkeycode(struct input_dev *dev,
- int scancode, int *keycode)
+ struct keycode_table_entry *kt_entry)
{
if (!dev->keycodesize)
return -EINVAL;

- if (scancode >= dev->keycodemax)
+ if (kt_entry->index >= dev->keycodemax)
return -EINVAL;

- *keycode = input_fetch_keycode(dev, scancode);
+ /*
+ * Supports only 8, 16 and 32 bit scancodes. It wouldn't be that
+ * hard to write some machine-endian logic to support 24 bit scancodes,
+ * but it seemed overkill. It should also be noticed that, since there
+ * are, in general, less than 256 scancodes sparsed into the scancode
+ * space, even with 16 bits, the codespace is sparsed, with leads into
+ * memory and code ineficiency, when retrieving the entire scancode
+ * space.
+ * So, it is highly recommended to implement getkeycodebig/setkeycodebig
+ * instead of using a normal table approach, when more than 8 bits is
+ * needed for the scancode.
+ *
+ */
+ switch (kt_entry->len) {
+ case 1:
+ if (kt_entry->index > ((1 << 8) - 1))
+ return -EINVAL;
+ *((u8 *)kt_entry->scancode) = (u8)kt_entry->index;
+ break;
+ case 2:
+ if (kt_entry->index > ((1 << 16) - 1))
+ return -EINVAL;
+ *((u16 *)kt_entry->scancode) = (u16)kt_entry->index;
+ break;
+ case 4:
+ *((u32 *)kt_entry->scancode) = kt_entry->index;
+ break;
+ default:
+ return -EINVAL;
+ }
+ kt_entry->keycode = input_fetch_keycode(dev, kt_entry->index);

return 0;
}

static int input_default_setkeycode(struct input_dev *dev,
- int scancode, int keycode)
+ struct keycode_table_entry *kt_entry)
{
int old_keycode;
int i;

- if (scancode >= dev->keycodemax)
+ if (kt_entry->index >= dev->keycodemax)
return -EINVAL;

if (!dev->keycodesize)
return -EINVAL;

- if (dev->keycodesize < sizeof(keycode) && (keycode >> (dev->keycodesize * 8)))
+ if (dev->keycodesize < sizeof(dev->keycode) &&
+ (kt_entry->keycode >> (dev->keycodesize * 8)))
return -EINVAL;

switch (dev->keycodesize) {
case 1: {
u8 *k = (u8 *)dev->keycode;
- old_keycode = k[scancode];
- k[scancode] = keycode;
+ old_keycode = k[kt_entry->index];
+ k[kt_entry->index] = kt_entry->keycode;
break;
}
case 2: {
u16 *k = (u16 *)dev->keycode;
- old_keycode = k[scancode];
- k[scancode] = keycode;
+ old_keycode = k[kt_entry->index];
+ k[kt_entry->index] = kt_entry->keycode;
break;
}
default: {
u32 *k = (u32 *)dev->keycode;
- old_keycode = k[scancode];
- k[scancode] = keycode;
+ old_keycode = k[kt_entry->index];
+ k[kt_entry->index] = kt_entry->keycode;
break;
}
}

clear_bit(old_keycode, dev->keybit);
- set_bit(keycode, dev->keybit);
+ set_bit(kt_entry->keycode, dev->keybit);

for (i = 0; i < dev->keycodemax; i++) {
if (input_fetch_keycode(dev, i) == old_keycode) {
@@ -629,6 +665,103 @@ static int input_default_setkeycode(struct input_dev *dev,
}

/**
+ * input_get_keycode_big - retrieve keycode currently mapped to a given scancode
+ * @dev: input device which keymap is being queried
+ * @kt_entry: keytable entry
+ *
+ * This function should be called by anyone interested in retrieving current
+ * keymap. Presently evdev handlers use it.
+ */
+int input_get_keycode_big(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry)
+{
+ if (dev->getkeycode) {
+ /*
+ * Support for legacy drivers, that don't implement the new
+ * ioctls: use index=scancode, just like the default methods
+ */
+ return dev->getkeycode(dev, kt_entry->index,
+ &kt_entry->keycode);
+ } else
+ return dev->getkeycodebig(dev, kt_entry);
+}
+EXPORT_SYMBOL(input_get_keycode_big);
+
+/**
+ * input_set_keycode_big - attribute a keycode to a given scancode
+ * @dev: input device which keymap is being queried
+ * @kt_entry: keytable entry
+ *
+ * This function should be called by anyone needing to update current
+ * keymap. Presently keyboard and evdev handlers use it.
+ */
+int input_set_keycode_big(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry)
+{
+ unsigned long flags;
+ int new_keycode, old_keycode;
+ int retval = -EINVAL;
+
+ if (kt_entry->keycode < 0 || kt_entry->keycode > KEY_MAX)
+ return -EINVAL;
+
+ spin_lock_irqsave(&dev->event_lock, flags);
+
+ new_keycode = kt_entry->keycode;
+
+ /*
+ * We need to know the old scancode, in order to generate a
+ * keyup effect, if the set operation happens successfully
+ */
+ if (dev->getkeycode) {
+ /*
+ * Support for legacy drivers, that don't implement the new
+ * ioctls: use index=scancode, just like the default methods
+ * If setkeycode is not defined, just return.
+ */
+ if (!dev->setkeycode)
+ goto out;
+
+ retval = dev->getkeycode(dev, kt_entry->index,
+ &kt_entry->keycode);
+ } else
+ retval = dev->getkeycodebig(dev, kt_entry);
+
+ old_keycode = kt_entry->keycode;
+ kt_entry->keycode = new_keycode;
+
+ if (retval)
+ goto out;
+
+ if (dev->getkeycode)
+ retval = dev->setkeycode(dev, kt_entry->index,
+ kt_entry->keycode);
+ else
+ retval = dev->setkeycodebig(dev, kt_entry);
+ if (retval)
+ goto out;
+
+ /*
+ * Simulate keyup event if keycode is not present
+ * in the keymap anymore
+ */
+ if (test_bit(EV_KEY, dev->evbit) &&
+ !is_event_supported(old_keycode, dev->keybit, KEY_MAX) &&
+ __test_and_clear_bit(old_keycode, dev->key)) {
+
+ input_pass_event(dev, EV_KEY, old_keycode, 0);
+ if (dev->sync)
+ input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+ }
+
+ out:
+ spin_unlock_irqrestore(&dev->event_lock, flags);
+
+ return retval;
+}
+EXPORT_SYMBOL(input_set_keycode_big);
+
+/**
* input_get_keycode - retrieve keycode currently mapped to a given scancode
* @dev: input device which keymap is being queried
* @scancode: scancode (or its equivalent for device in question) for which
@@ -640,10 +773,33 @@ static int input_default_setkeycode(struct input_dev *dev,
*/
int input_get_keycode(struct input_dev *dev, int scancode, int *keycode)
{
- if (scancode < 0)
- return -EINVAL;
+ if (dev->getkeycode) {
+ /*
+ * Use the legacy calls
+ */
+ return dev->getkeycode(dev, scancode, keycode);
+ } else {
+ int retval;
+ char char_scan[4];
+ struct keycode_table_entry kt_entry;
+
+ /*
+ * Userspace is using a legacy call with a driver ported
+ * to the new way. This is a bad idea with long sparsed
+ * tables, since lots of the retrieved values will be in
+ * blank. Also, it makes sense only if the table size is
+ * lower than 2^32.
+ */
+ memset(&kt_entry, 0, sizeof(kt_entry));
+ kt_entry.len = 32;
+ kt_entry.index = scancode;
+ kt_entry.scancode = char_scan;
+
+ retval = dev->getkeycodebig(dev, &kt_entry);

- return dev->getkeycode(dev, scancode, keycode);
+ *keycode = kt_entry.keycode;
+ return retval;
+ }
}
EXPORT_SYMBOL(input_get_keycode);

@@ -662,21 +818,48 @@ int input_set_keycode(struct input_dev *dev, int scancode, int keycode)
int old_keycode;
int retval;

- if (scancode < 0)
- return -EINVAL;
-
if (keycode < 0 || keycode > KEY_MAX)
return -EINVAL;

spin_lock_irqsave(&dev->event_lock, flags);

- retval = dev->getkeycode(dev, scancode, &old_keycode);
- if (retval)
- goto out;
+ if (dev->getkeycode) {
+ /*
+ * Use the legacy calls
+ */
+ retval = dev->getkeycode(dev, scancode, &old_keycode);
+ if (retval)
+ goto out;

- retval = dev->setkeycode(dev, scancode, keycode);
- if (retval)
- goto out;
+ retval = dev->setkeycode(dev, scancode, keycode);
+ if (retval)
+ goto out;
+ } else {
+ char char_scan[4];
+ struct keycode_table_entry kt_entry;
+
+ /*
+ * Userspace is using a legacy call with a driver ported
+ * to the new way. This is a bad idea with long sparsed
+ * tables, since lots of the retrieved values will be in
+ * blank. Also, it makes sense only if the table size is
+ * lower than 2^32.
+ */
+ memset(&kt_entry, 0, sizeof(kt_entry));
+ kt_entry.len = 32;
+ kt_entry.index = scancode;
+ kt_entry.scancode = char_scan;
+
+ retval = dev->getkeycodebig(dev, &kt_entry);
+ if (retval)
+ goto out;
+
+ kt_entry.keycode = keycode;
+
+ retval = dev->setkeycodebig(dev, &kt_entry);
+ if (retval)
+ goto out;
+ }

/*
* Simulate keyup event if keycode is not present
@@ -1585,11 +1768,11 @@ int input_register_device(struct input_dev *dev)
dev->rep[REP_PERIOD] = 33;
}

- if (!dev->getkeycode)
- dev->getkeycode = input_default_getkeycode;
+ if (!dev->getkeycodebig)
+ dev->getkeycodebig = input_default_getkeycode;

- if (!dev->setkeycode)
- dev->setkeycode = input_default_setkeycode;
+ if (!dev->setkeycodebig)
+ dev->setkeycodebig = input_default_setkeycode;

dev_set_name(&dev->dev, "input%ld",
(unsigned long) atomic_inc_return(&input_no) - 1);
diff --git a/include/linux/input.h b/include/linux/input.h
index 663208a..1f86f70 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -34,7 +34,7 @@ struct input_event {
* Protocol version.
*/

-#define EV_VERSION 0x010000
+#define EV_VERSION 0x010001

/*
* IOCTLs (0x00 - 0x7f)
@@ -56,12 +56,22 @@ struct input_absinfo {
__s32 resolution;
};

+struct keycode_table_entry {
+ __u32 keycode; /* e.g. KEY_A */
+ __u32 index; /* Index for the given scan/key table */
+ __u32 len; /* Lenght of the scancode */
+ __u32 reserved[2]; /* Reserved for future usage */
+ char *scancode; /* scancode, in machine-endian */
+};
+
#define EVIOCGVERSION _IOR('E', 0x01, int) /* get driver version */
#define EVIOCGID _IOR('E', 0x02, struct input_id) /* get device ID */
#define EVIOCGREP _IOR('E', 0x03, int[2]) /* get repeat settings */
#define EVIOCSREP _IOW('E', 0x03, int[2]) /* set repeat settings */
#define EVIOCGKEYCODE _IOR('E', 0x04, int[2]) /* get keycode */
#define EVIOCSKEYCODE _IOW('E', 0x04, int[2]) /* set keycode */
+#define EVIOCGKEYCODEBIG _IOR('E', 0x04, struct keycode_table_entry) /* get keycode */
+#define EVIOCSKEYCODEBIG _IOW('E', 0x04, struct keycode_table_entry) /* set keycode */

#define EVIOCGNAME(len) _IOC(_IOC_READ, 'E', 0x06, len) /* get device name */
#define EVIOCGPHYS(len) _IOC(_IOC_READ, 'E', 0x07, len) /* get physical location */
@@ -1022,11 +1032,15 @@ struct ff_effect {
* @keycodemax: size of keycode table
* @keycodesize: size of elements in keycode table
* @keycode: map of scancodes to keycodes for this device
- * @setkeycode: optional method to alter current keymap, used to implement
+ * @setkeycode: optional legacy method to alter current keymap, used to
+ * implement sparse keymaps. Shouldn't be used on new drivers
+ * @getkeycode: optional legacy method to retrieve current keymap.
+ * Shouldn't be used on new drivers.
+ * @setkeycodebig: optional method to alter current keymap, used to implement
* sparse keymaps. If not supplied default mechanism will be used.
* The method is being called while holding event_lock and thus must
* not sleep
- * @getkeycode: optional method to retrieve current keymap. If not supplied
+ * @getkeycodebig: optional method to retrieve current keymap. If not supplied
* default mechanism will be used. The method is being called while
* holding event_lock and thus must not sleep
* @ff: force feedback structure associated with the device if device
@@ -1101,6 +1115,10 @@ struct input_dev {
void *keycode;
int (*setkeycode)(struct input_dev *dev, int scancode, int keycode);
int (*getkeycode)(struct input_dev *dev, int scancode, int *keycode);
+ int (*setkeycodebig)(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry);
+ int (*getkeycodebig)(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry);

struct ff_device *ff;

@@ -1366,6 +1384,11 @@ static inline void input_set_abs_params(struct input_dev *dev, int axis, int min

int input_get_keycode(struct input_dev *dev, int scancode, int *keycode);
int input_set_keycode(struct input_dev *dev, int scancode, int keycode);
+int input_get_keycode_big(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry);
+int input_set_keycode_big(struct input_dev *dev,
+ struct keycode_table_entry *kt_entry);
+

extern struct class input_class;