On Sun, Aug 02, 2020 at 07:28:00PM +0200, Saheed Bolarinwa wrote:
Because the value ~0 has a meaning to some drivers and only
No, ~0 means that the PCI read failed. For *every* PCI device I know.
Here's me reading from 0xf0 offset of my hostbridge:
# setpci -s 00:00.0 0xf0.l 01000000
That device doesn't have extended config space, so the last valid byte is 0xff. Let's read beyond that:
# setpci -s 00:00.0 0x100.l ffffffff
Again, only the drivers can determine if ~0 is a valid value. This information is not available inside pci_config_read*().
Of course it is.
*every* change you've done in 6/17 - this is the only patch I have received - checks for == ~0. So that check can just as well be moved inside pci_config_read_*().
Here's how one could do it:
#define PCI_OP_READ(size, type, len) \ int noinline pci_bus_read_config_##size \ (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \ { \ int res; \ unsigned long flags; \ u32 data = 0; \ if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \ pci_lock_config(flags); \ res = bus->ops->read(bus, devfn, pos, len, &data); \
/* Check we actually read something which is not all 1s.*/ if (data == ~0) return PCIBIOS_READ_FAILED;
*value = (type)data; \ pci_unlock_config(flags); \ return res; \ }
Also, I'd prefer a function to *not* return void but return either an error or success. In the success case, the @value argument can be consumed by the caller and otherwise not.
In any case, that change is a step in the wrong direction and I don't like it, sorry.