On Feb 11, 2013, at 10:08 AM, "David F." <df7...@gmail.com> wrote:
> Hmm, but is the driver name in a fixed format that will indicate the device
> type?
The component name is a free form unicode string that can support multiple
languages.
> Or am I going to be stuck having to do a bunch of if ata/atapi type device
> then send identify device command, if it's scsi, send inquiry, if usb, do
> that, if it's 1394, do something else, etc.. The basic IO to the device
> seems to be abstract as well as the scsi passthrough seems like it would be
> able to handle atapi, 1394, usb, and scsi devices (those all using scsi
> cdb's) for special commands.
The device path needs to understand the bus, but not the type of device. You
need to understand the bus to distinguish between the different devices on the
bus.
> But I'd really like/need to know the basic device type, is it tape, cd/dvd/bd
> type, hard drive (dasd) , floppy, some other type? I may want to only handle
> a certain type in a certain way and not touch the others...
>
>
Your example list is why we chose not to try and describe devices. DASD is the
anachronistic IBM term that includes magnetic drums and data cells (it is nice
to talk about some technology that is actually older than me for a change). Do
people still use floppy disks? CD/DVD/BD are becoming less popular....
Thanks,
Andrew Fish
> On Mon, Feb 11, 2013 at 9:46 AM, Andrew Fish <af...@apple.com> wrote:
>
> On Feb 9, 2013, at 11:51 AM, David F. <df7...@gmail.com> wrote:
>
> > Hi,
> >
> > I see lots of good information in device paths, I expected to see a "device
> > type" but don't?? So maybe in a block protocol of some type, but couldn't
> > find it. How are you supposed to determine the device type in a generic
> > way - similar to scsi device types 0 = DASD (or hard drive), 5 =
> > cdrom/dvd/etc..., etc... ? Is there some EFI_DEV_TYPE_PROTOCOL that can be
> > queried to get that (floppy, cd, hard drive, other block devices)?
> >
>
> The device path was intended as something that could be stored in NVRAM and
> be valid from boot to boot. So for example the PCI bus is not stored in the
> device path as it can change from boot to boot (just Dev/Func from the root).
> The device path is also used to communicate with the OS about what devices
> should be consoles or boot options. But the focus of the device path is a
> programatic path to talk to the device.
>
> We decided to not be like legacy BIOS and try and make assumptions about the
> hardware in the system. So from a UI perspective there is the Component Name
> protocol that returns a Unicode string that describes the devices. This way
> technology can advance and the specification does not need to keep changing.
>
> There is a chapter in UEFI specification about device paths and there is also
> info on component name. http://www.uefi.org/specs/
>
> Thanks,
>
> Andrew Fish
>
> > TIA!!
> >
> >
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