Commit 3880729a authored by Marc Zyngier's avatar Marc Zyngier Committed by Christoph Hellwig

[PATCH] EISA/sysfs update

Here is the latest round of EISA/sysfs update.

 - Add documentation,
 - Add support for per EISA-id driver data,
 - Move virtual_root device to a platform device,
 - Update CREDITS.
parent 384ceab5
......@@ -3492,9 +3492,9 @@ S: Italy
N: Marc Zyngier
E: maz@wild-wind.fr.eu.org
W: http://www.misterjones.org
D: MD driver
S: 11 rue Victor HUGO
S: 95560 Montsoult
D: EISA/sysfs subsystem
S: France
# Don't add your name here, unless you really _are_ after Marc
......
EISA bus support (Marc Zyngier <maz@wild-wind.fr.eu.org>)
This document groups random notes about porting EISA drivers to the
new EISA/sysfs API.
Starting from version 2.5.59, the EISA bus is almost given the same
status as other much more mainstream busses such as PCI or USB. This
has been possible through sysfs, which defines a nice enough set of
abstractions to manage busses, devices and drivers.
Although the new API is quite simple to use, converting existing
drivers to the new infrastructure is not an easy task (mostly because
detection code is generally also used to probe ISA cards). Moreover,
most EISA drivers are among the oldest Linux drivers so, as you can
imagine, some dust has settled here over the years.
The EISA infrastructure is made up of three parts :
- The bus code implements most of the generic code. It is shared
among all the architectures that the EISA code runs on. It
implements bus probing (detecting EISA cards avaible on the bus),
allocates I/O resources, allows fancy naming through sysfs, and
offers interfaces for driver to register.
- The bus root driver implements the glue between the bus hardware
and the generic bus code. It is responsible for discovering the
device implementing the bus, and setting it up to be latter probed
by the bus code. This can go from something as simple as reserving
an I/O region on x86, to the rather more complex, like the hppa
EISA code. This is the part to implement in order to have EISA
running on an "new" platform.
- The driver offers the bus a list of devices that it manages, and
implements the necessary callbacks to probe and release devices
whenever told to.
Every function/structure below lives in <linux/eisa.h>, which depends
heavily on <linux/device.h>.
** Bus root driver :
int eisa_root_register (struct eisa_root_device *root);
The eisa_root_register function is used to declare a device as the
root of an EISA bus. The eisa_root_device structure holds a reference
to this device, as well as some parameters for probing purposes.
struct eisa_root_device {
struct list_head node;
struct device *dev; /* Pointer to bridge device */
struct resource *res;
unsigned long bus_base_addr;
int slots; /* Max slot number */
int bus_nr; /* Set by eisa_root_register */
};
node : used for eisa_root_register internal purpose
dev : pointer to the root device
res : root device I/O resource
bus_base_addr : slot 0 address on this bus
slots : max slot number to probe
bus_nr : unique bus id, set by eisa_root_register
** Driver :
int eisa_driver_register (struct eisa_driver *edrv);
void eisa_driver_unregister (struct eisa_driver *edrv);
Clear enough ?
struct eisa_device_id {
char sig[EISA_SIG_LEN];
unsigned long driver_data;
};
struct eisa_driver {
const struct eisa_device_id *id_table;
struct device_driver driver;
};
id_table : an array of NULL terminated EISA id strings,
followed by an empty string. Each string can be
paired with a driver-dependant value (driver_data).
driver : a generic driver, such as described in
Documentation/driver-model/driver.txt. Only .name,
.probe and .remove members are mandatory.
An example is the 3c509 driver :
struct eisa_device_id el3_eisa_ids[] = {
{ "TCM5092" },
{ "TCM5093" },
{ "" }
};
struct eisa_driver el3_eisa_driver = {
.id_table = el3_eisa_ids,
.driver = {
.name = "3c509",
.probe = el3_eisa_probe,
.remove = __devexit_p (el3_device_remove)
}
};
** Device :
The sysfs framework calls .probe and .remove functions upon device
discovery and removal (note that the .remove function is only called
when driver is built as a module).
Both functions are passed a pointer to a 'struct device', which is
encapsulated in a 'struct eisa_device' described as follows :
struct eisa_device {
struct eisa_device_id id;
int slot;
unsigned long base_addr;
struct resource res;
struct device dev; /* generic device */
};
id : EISA id, as read from device. id.driver_data is set from the
matching driver EISA id.
slot : slot number which the device was detected on
res : I/O resource allocated to this device
dev : generic device (see Documentation/driver-model/device.txt)
You can get the 'struct eisa_device' from 'struct device' using the
'to_eisa_device' macro.
** Misc stuff :
void eisa_set_drvdata (struct eisa_device *edev, void *data);
Stores data into the device's driver_data area.
void *eisa_get_drvdata (struct eisa_device *edev):
Gets the pointer previously stored into the device's driver_data area.
** Random notes :
Converting an EISA driver to the new API mostly involves *deleting*
code (since probing is now in the core EISA code). Unfortunately, most
drivers share their probing routine between ISA, MCA and EISA. Special
care must be taken when ripping out the EISA code, so other busses
won't suffer from these surgical strikes...
You *must not* expect any EISA device to be detected when returning
from eisa_driver_register, since the chances are that the bus has not
yet been probed. In fact, that's what happens most of the time (the
bus root driver usually kicks in rather late in the boot process).
Unfortunately, most drivers are doing the probing by themselves, and
expect to have explored the whole machine when they exit their probe
routine.
** Thanks :
I'd like to thank the following people for their help :
- Xavier Benigni for lending me a wonderful Alpha Jensen,
- James Bottomley, Jeff Garzik for getting this stuff into the kernel,
- Andries Brouwer for contributing numerous EISA ids,
- Catrin Jones for coping with too many machines at home
......@@ -83,8 +83,10 @@ static int eisa_bus_match (struct device *dev, struct device_driver *drv)
return 0;
while (strlen (eids->sig)) {
if (!strcmp (eids->sig, edev->id.sig))
if (!strcmp (eids->sig, edev->id.sig)) {
edev->id.driver_data = eids->driver_data;
return 1;
}
eids++;
}
......
......@@ -13,14 +13,19 @@
#include <linux/module.h>
#include <linux/init.h>
/* The default EISA device parent (virtual root device). */
static struct device eisa_root_dev = {
/* The default EISA device parent (virtual root device).
* Now use a platform device, since that's the obvious choice. */
static struct platform_device eisa_root_dev = {
.name = "eisa",
.id = 0,
.dev = {
.name = "Virtual EISA Bridge",
.bus_id = "eisa",
},
};
static struct eisa_root_device eisa_bus_root = {
.dev = &eisa_root_dev,
.dev = &eisa_root_dev.dev,
.bus_base_addr = 0,
.res = &ioport_resource,
.slots = EISA_MAX_SLOTS,
......@@ -30,16 +35,16 @@ static int virtual_eisa_root_init (void)
{
int r;
if ((r = device_register (&eisa_root_dev))) {
if ((r = platform_device_register (&eisa_root_dev))) {
return r;
}
eisa_root_dev.driver_data = &eisa_bus_root;
eisa_root_dev.dev.driver_data = &eisa_bus_root;
if (eisa_root_register (&eisa_bus_root)) {
/* A real bridge may have been registered before
* us. So quietly unregister. */
device_unregister (&eisa_root_dev);
platform_device_unregister (&eisa_root_dev);
return -1;
}
......
......@@ -21,6 +21,7 @@
/* The EISA signature, in ASCII form, null terminated */
struct eisa_device_id {
char sig[EISA_SIG_LEN];
unsigned long driver_data;
};
/* There is not much we can say about an EISA device, apart from
......
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