Ugh. Trying to work out how to write "static" functions for sysfs attributes. You know, you just want to say, "Export this specific field in this structure. It's a u16 and I don't want to be notified when someone reads it."

Today you have to write a bit of code for every single thing that you want to export in sysfs. For structures with a lot of different fields, you end up doing some fun with #defines that would make any sane programmer cringe if they noticed it. For example, look at this fun stuff I wrote in the PCI core code in the kernel:

/* show configuration fields */
#define pci_config_attr(field, format_string)                           \
static ssize_t                                                          \
field##_show(struct device *dev, char *buf)                             \
{                                                                       \
        struct pci_dev *pdev;                                           \
                                                                        \
        pdev = to_pci_dev (dev);                                        \
        return sprintf (buf, format_string, pdev->field);               \
}

pci_config_attr(vendor, "0x%04x\n");
pci_config_attr(device, "0x%04x\n");
pci_config_attr(subsystem_vendor, "0x%04x\n");
pci_config_attr(subsystem_device, "0x%04x\n");
pci_config_attr(class, "0x%06x\n");
pci_config_attr(irq, "%u\n");

See what I mean? That's about the cleanest way I've seen this done, and even then, we're burning a function per attribute.

But hey, it's way better than anything you ever did with /proc, but still, it could be made easier. So that's why I'm trying to make it easier...

posted Thu, 16 Sep 2004 in [/diary]