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SubjectRe: [RFC-patch 1/3] SuperIO locks coordinator
On Thu, 14 Sep 2006 01:13:03 -0600 Jim Cromie wrote:

> diff -ruNp -X dontdiff -X exclude-diffs 6locks-1/drivers/isa/Kconfig 6locks-2/drivers/isa/Kconfig
> --- 6locks-1/drivers/isa/Kconfig 1969-12-31 17:00:00.000000000 -0700
> +++ 6locks-2/drivers/isa/Kconfig 2006-09-13 09:54:18.000000000 -0600
> @@ -0,0 +1,7 @@
> +
> +config SUPERIO_LOCKS
> + tristate "Super-IO port sharing"
> + help
> + this module provides locks for use by drivers which need to

This

> + share access to a multi-function device via its superio port,
> + and which register that port.

> diff -ruNp -X dontdiff -X exclude-diffs 6locks-1/drivers/isa/superio_locks.c 6locks-2/drivers/isa/superio_locks.c
> --- 6locks-1/drivers/isa/superio_locks.c 1969-12-31 17:00:00.000000000 -0700
> +++ 6locks-2/drivers/isa/superio_locks.c 2006-09-13 14:56:32.000000000 -0600
> @@ -0,0 +1,169 @@
> +
> +/**
> + module provides a means for modules to register their use of a
> + Super-IO port, and provides an access-lock for the registering
> + modules to use to coordinate with each other. Consider it a
> + parking-attendant's key-board. Design is perhaps ISA centric,
> + maybe formalize this, with (platform|isa)_driver.
> +*/

Two comments about that comment:

a. Kernel long-comment style is:

/*
* This module provides a means for modules to register
* their use of a Super-IO port, ...
*/

b. Don't use "/**" to begin a comment block unless the comment block
contains kernel-doc formatted comments. (This one does not.)


> +
> +/* superio_get() checks whether the expected SuperIO device is
> + present at a specific cmd-addr. Use in loop to scan.
> +*/

For functions that are not static (and when you want this merged,
not just RFC), please include kernel-doc comments describing the
function and its parameters. See Documentation/kernel-doc-nano-HOWTO.txt
for more info.

> +struct superio* superio_get(u16 cmd_addr, u8 dev_id_addr,
> + u8 want_devid)
> +{
> + int slot, rc, mydevid;
> +
> + mutex_lock(&reservation_lock);
> +
> + /* share any already allocated lock for this cmd_addr, device-id */
> + for (slot = 0; slot < max_locks; slot++) {
> + if (sio_locks[slot].users
> + && cmd_addr == sio_locks[slot].sioaddr
> + && want_devid == sio_locks[slot].devid) {
> +
> + if (sio_locks[slot].users == 255) {
> + dprintk("too many drivers sharing port %x\n", cmd_addr);
> + mutex_unlock(&reservation_lock);
> + return 0;
> + }
> + sio_locks[slot].users++;
> + dprintk("sharing port:%x dev:%x users:%d\n",
> + cmd_addr, want_devid, sio_locks[slot].users);
> + mutex_unlock(&reservation_lock);
> + return &sio_locks[slot];
> + }
> + }
> + /* read the device-id-address */
> + outb(dev_id_addr, cmd_addr);
> + mydevid = inb(cmd_addr+1);
> +
> + /* but 1st, check that the cmd register remembers the val just written */
> + rc = inb(cmd_addr);
> + if (rc != dev_id_addr) {
> + dprintk("superio_cmdaddr %x absent %d\n", cmd_addr, rc);
> + mutex_unlock(&reservation_lock);
> + return NULL;
> + }
> + /* test for the desired device id value */
> + if (mydevid != want_devid) {
> + mutex_unlock(&reservation_lock);
> + return NULL;
> + }
> + /* find 1st unused slot */
> + for (slot = 0; slot < max_locks; slot++)
> + if (!sio_locks[slot].users)
> + break;
> +
> + if (slot >= max_locks) {
> + printk(KERN_ERR "No superio-locks left. increase max_locks\n");
> + mutex_unlock(&reservation_lock);
> + return NULL;
> + }
> + dprintk("allocating slot %d, addr %x for device %x\n",
> + slot, cmd_addr, want_devid);
> +
> + sio_locks[slot].sioaddr = cmd_addr;
> + sio_locks[slot].devid = want_devid;
> + sio_locks[slot].users = 1;
> + num_locks++;
> +
> + mutex_unlock(&reservation_lock);
> + return &sio_locks[slot];
> +}
> +EXPORT_SYMBOL_GPL(superio_get);
> +
> +/* array args must be null terminated */

Also needs kernel-doc function comment header.

> +struct superio* superio_find(u16 cmd_addrs[], u8 devid_addr,
> + u8 want_devids[])
> +{
> + int i, j;
> + struct superio* gate;
> +
> + for (i = 0; cmd_addrs[i]; i++) {
> + for (j = 0; want_devids[j]; j++) {
> + gate = superio_get(cmd_addrs[i], devid_addr,
> + want_devids[j]);
> + if (gate) {
> + dprintk("found devid:%x port:%x\n",
> + want_devids[j], cmd_addrs[i]);
> + return gate;
> + } else
> + dprintk("no devid:%x at port:%x\n",
> + want_devids[j], cmd_addrs[i]);
> + }
> + }
> + return NULL;
> +}
> +EXPORT_SYMBOL_GPL(superio_find);
> +
> +void superio_release(struct superio* const gate)

Ditto.

> +{
> + if (gate < &sio_locks[0] || gate >= &sio_locks[max_locks]) {
> + printk(KERN_ERR
> + " superio: attempt to release corrupted superio-lock"
> + " %p vs %p\n", gate, &sio_locks);
> + return;
> + }
> + if (!(--gate->users))
> + dprintk("releasing last user of superio-port %x\n", gate->sioaddr);
> + return;
> +}
> +EXPORT_SYMBOL_GPL(superio_release);
> +

> diff -ruNp -X dontdiff -X exclude-diffs 6locks-1/include/linux/superio-locks.h 6locks-2/include/linux/superio-locks.h
> --- 6locks-1/include/linux/superio-locks.h 1969-12-31 17:00:00.000000000 -0700
> +++ 6locks-2/include/linux/superio-locks.h 2006-09-13 14:21:08.000000000 -0600
> @@ -0,0 +1,55 @@
> +#include <linux/mutex.h>
> +#include <asm/io.h>
> +
> +/* Super-IO ports are found in low-pin-count hardware (typically ISA,
> + any others ?). They usually provide access to many functional
> + units, so many drivers must share the superio port. This struct
> + provides a lock that allows the drivers to coordinate access to that
> + port.
> +*/
Use long-comment style, please.

> +struct superio {
> + struct mutex lock; /* lock shared amongst user drivers */
> + u16 sioaddr; /* port's tested cmd-address */
> + u8 devid; /* devid found by the registering driver */
> + u8 users; /* I cant imagine >256 user drivers */
> +};
> +
> +/* array args must be null terminated */
> +struct superio* superio_find(u16 sioaddrs[], u8 devid_addr, u8 devid_vals[]);
> +struct superio* superio_get(u16 sioaddr, u8 devid_addr, u8 devid_val);
> +void superio_release(struct superio* const gate);
> +
> +/* these locking ops do not address the idling & activation of some
> + superio devices, which will, once 'locked', ignore accesses until
> + the 'unlock' sequence is done 1st. Unfortunately these sequences
> + vary by device, and in any case don't protect 2 drivers from
> + stepping on each other's operations.
> +
> + Callbacks are a possible approach, but every driver using a device
> + would have to provide them, and only the 1st loaded module would
> + actually succeed in registering them. Furthermore, if any driver
> + accessing a port uses the idle/activate sequences, they all must.
> + On the whole, this is complexity w/o benefit.
> +*/

long-comment style, please.

---
~Randy
-
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