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 device   *dev;    /* Pointer to bridge device */
        struct resource *res;
        unsigned long    bus_base_addr;
        int              slots;  /* Max slot number */
        int              force_probe; /* Probe even when no slot 0 */
        u64              dma_mask; /* from bridge device */
        int              bus_nr; /* Set by eisa_root_register */
        struct resource  eisa_root_res; /* ditto */
};

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;
};

An example is the 3c59x driver:

static struct eisa_device_id vortex_eisa_ids[] = {
        { "TCM5920", EISA_3C592_OFFSET },
        { "TCM5970", EISA_3C597_OFFSET },
        { "" }
};

static struct eisa_driver vortex_eisa_driver = {
        .id_table = vortex_eisa_ids,
        .driver   = {
                .name    = "3c59x",
                .probe   = vortex_eisa_probe,
                .remove  = vortex_eisa_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;
        int                   state;
        unsigned long         base_addr;
        struct resource       res[EISA_MAX_RESOURCES];
        u64                   dma_mask;
        struct device         dev; /* generic device */
};

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.

int eisa_get_region_index (void *addr);

Returns the region number (0 <= x < EISA_MAX_RESOURCES) of a given address.

Kernel parameters¶

eisa_bus.enable_dev

A comma-separated list of slots to be enabled, even if the firmware set the card as disabled. The driver must be able to properly initialize the device in such conditions.

eisa_bus.disable_dev

A comma-separated list of slots to be disabled, even if the firmware set the card as enabled. The driver won’t be called to handle this device.

virtual_root.force_probe

Force the probing code to probe EISA slots even when it cannot find an EISA compliant mainboard (nothing appears on slot 0). Defaults to 0 (don’t force), and set to 1 (force probing) when CONFIG_EISA_VLB_PRIMING is set.

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, and EISA. Special care must be taken when ripping out the EISA code, so other buses 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.

For example, switching your favorite EISA SCSI card to the “hotplug” model is “the right thing”(tm).

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 far too many machines at home.