Re: How to open a file by it's full path in UEFI

[GN Keshava <keshava.gn@gmail.com>]

Hi Laszlo,

Thanks for the reply. I meant I have complete file path. I believe the
"device path" is different. Is it possible to obtain DevicePath using my
full file path?

Thanks.
Regards,
Keshava

On Tue, 27 Sep 2016 at 14:46 Laszlo Ersek <lersek@redhat.com> wrote:

> On 09/27/16 11:03, GN Keshava wrote:
> > Hi all,
> >
> >
> > I'm trying to open a file from my UEFI application. The path of file is
> >
> > fs1:/myfolder/myfile.txt
> >
> > The code :
> >
> > efiStatus = bs->LocateHandleBuffer(ByProtocol,
> >                                    &sfspGuid,
> >                                    NULL,
> >                                    &handleCount,
> >                                    &handles);
> >
> > for (index = 0; index < (int)handleCount; ++ index)
> > {
> >     EFI_SIMPLE_FILE_SYSTEM_PROTOCOL* fs = NULL;
> >
> >     efiStatus = bs->HandleProtocol(
> >         handles[index],
> >         &sfspGuid,
> >         (void**)&fs);
> >
> >     EFI_FILE_PROTOCOL* root = NULL;
> >     ...
> >     efiStatus = fs->OpenVolume(fs, &root);
> >
> >     EFI_FILE_PROTOCOL* token = NULL;
> >
> >     efiStatus = root->Open(
> >         root,
> >         &token,
> >         L"myfolder\\myfile.txt",
> >         EFI_FILE_MODE_READ,
> >         EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN | EFI_FILE_SYSTEM);
> > }
> >
> > But using this method, I can only go through all the file system handles
> > and open each volume and try opening my file.
> >
> > But I want to give full path to my file and open it in it's volume.
> >
> > How can I acheive this?
> > Thanks.
>
> If you have a complete device path, you can use gBS->LocateDevicePath()
> with gEfiSimpleFileSystemProtocolGuid, to locate the handle with the
> most specific device path (--> the longest device path prefix) with the
> simple FS protocol installed on it. Then you can check if the remaining
> device path (returned by the service) consist of nothing but one File
> Path Media Device Path node. If so, you can open the simple FS protocol
> on the handle found, then use that to open the file by pathname.
>
> Laszlo
>
>