Re: ioremap of pci base addresses

From: Francois romieu (
Date: Thu Oct 12 2000 - 05:52:00 EST

The Thu, Oct 12, 2000 at 11:02:50AM +0530, wrote :
> once i have got the pci_dev structure( by calling pci_find*), do i
> explicitly need to call ioremap for remapping mmio.
> i think pci_enable_device does this. correct me if i am wrong..

ioremap does not only remap mmio but returns a token that should be
used if you want to further access the mmapped area (readl(token) and
writel(some_data, token) for example).

Part of 'foo' code could look like this :

static struct pci_driver foo_driver = {
        name: "foo",
        id_table: foo_pci_tbl,
        probe: foo_init_one,
        remove: foo_remove_one,

static int __init foo_init_one (struct pci_dev *pdev,
                                struct pci_device_id *ent)
        u32 token;

        if (pci_enable_device(pdev))
                goto err_out;

         * Some area (non pci-configuration registers or other) one wants to
         * mmap. Ask 'foo' manual for the description of the Base Address
         * Register in foo's pci configuration space.
        if (!request_mem_region(pci_resource_start(pdev, 0),
                                pci_resource_len(pdev, 0), "mmaped registers")) {
                printk(KERN_ERR "foo: can't reserve MMIO region\n");
                goto err_out;
        token = = (unsigned long)ioremap(pci_resource_start(pdev, 0),
                                          pci_resource_len(pdev, 0));

         * The following will happen if one forgets to balance ioremap
         * and iounmap at insmod/rmmod time for example.
        if (!token) {
                printk(KERN_ERR "foo: cannot remap MMIO region %lx @ %lx\n",
                       pci_resource_len(pdev, 0), pci_resource_start(pdev, 0));
                goto err_out_free_mmio_region;

        [more stuff that may fail and should go at least to label err_out_iounmap]

        return 0;

        iounmap ((void *)token);
        release_mem_region(pci_resource_start(pdev, 0),
                           pci_resource_len(pdev, 0));
        return -ENODEV;

static void foo_remove_one (struct pci_dev *pdev)
        [some stuff]

        iounmap((void *)some_safe_structure->token);

        [kfree may appear...]

        release_mem_region(pci_resource_start(pdev, 0),
                           pci_resource_len(pdev, 0));

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