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

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

Thanks, Andrew, Laurie, Laszlo, Jaben, for quick help!! :)

Regards,
Keshava

On Tue 27 Sep, 2016 10:18 pm Andrew Fish, <afish@apple.com> wrote:

> I was kind of surprised that an example like this did not exist in:
> https://github.com/tianocore/edk2/tree/master/ShellPkg/Application
>
> Thanks,
>
> Andrew Fish
>
> > On Sep 27, 2016, at 9:44 AM, Jarlstrom, Laurie <
> laurie.jarlstrom@intel.com> wrote:
> >
> > Keshava,
> > Attached Sample code  is an example that will open a file name passed
> through the command line using the Shell.
> >
> >
> > thanks,
> > Laurie
> >
> > laurie.jarlstrom@intel.com
> >
> > Intel SSG/STO/EBP
> > (503) 712-9395
> >
> >
> >
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> GN Keshava
> > Sent: Tuesday, September 27, 2016 4:52 AM
> > To: Laszlo Ersek
> > Cc: edk2-devel@lists.01.org
> > Subject: Re: [edk2] How to open a file by it's full path in UEFI
> >
> > Thank you Laszlo.
> >
> > I'll check it out. :)
> >
> > Thanks again.
> > Regards,
> > Keshava
> >
> > On Tue, 27 Sep 2016 at 16:47 Laszlo Ersek <lersek@redhat.com> wrote:
> >
> >> On 09/27/16 12:46, GN Keshava wrote:
> >>> Hi Laszlo,
> >>>
> >>> Thank you for the answer. It was helpful.
> >>>
> >>> Considering option #1, can you give some more details (a small
> >>> example or any reference link would be helpful), how I can use Shell
> >>> APIs in my C file (which will compile to my .efi app)?
> >>
> >> Hmmm, I don't have hands-on experience with this, but you might want
> >> to try the ShellOpenFileByName() function, from
> >> "ShellPkg/Include/Library/ShellLib.h".
> >>
> >> You can find examples for UEFI applications that use the Shell library
> >> with:
> >>
> >>  git grep -w ShellLib -- '*inf'
> >>
> >> or just grep the tree for ShellOpenFileByName().
> >>
> >> See also "AppPkg/ReadMe.txt".
> >>
> >>> Considering option #2, How I can find device path programatically
> >>> from my C file?
> >>
> >> The EFI_SHELL_PROTOCOL.GetDevicePathFromMap() member function seems
> >> relevant -- it is specified in the UEFI Shell spec --, but I would
> >> definitely try ShellOpenFileByName() first.
> >>
> >> Thanks
> >> Laszlo
> >>
> >>> Thanks again for the help. :)
> >>> With regards,
> >>> Keshava
> >>>
> >>> On Tue, 27 Sep 2016 at 15:19 Laszlo Ersek <lersek@redhat.com
> >>> <mailto:lersek@redhat.com>> wrote:
> >>>
> >>>    On 09/27/16 11:25, GN Keshava wrote:
> >>>> 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?
> >>>
> >>>    The pathname you seem to have (as "complete") is specific to a given
> >>>    simple FS, so system-wide it cannot be considered complete
> >>> (there
> >> can be
> >>>    multiple filesystems).
> >>>
> >>>    In your original email I missed that you started with "FS1:".
> >> Andrew's
> >>>    answer covers that case.
> >>>
> >>>    In summary, you can do three things:
> >>>    - have a pathname that starts with FSx: (which is a shell-specific
> >>>    mapping), and use Andrew's recommendation,
> >>>    - have a complete UEFI device path, and then use what I recommended,
> >>>    - have no information for selecting the filesystem (from the many
> >>>    possible), and use your current iteration.
> >>>
> >>>    Options #1 and #2 actually correspond to each other, considering
> >>>    "expressive power" / information content (as long as you are in the
> >>>    shell); please see the MAP shell command.
> >>>
> >>>    Thanks
> >>>    Laszlo
> >>>
> >>>> On Tue, 27 Sep 2016 at 14:46 Laszlo Ersek <lersek@redhat.com
> >>>    <mailto:lersek@redhat.com>
> >>>> <mailto:lersek@redhat.com <mailto: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
> >>>>
> >>>
> >>
> >>
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