From: GN Keshava <keshava.gn@gmail.com>
To: Laszlo Ersek <lersek@redhat.com>
Cc: "edk2-devel@lists.01.org" <edk2-devel@ml01.01.org>
Subject: Re: How to open a file by it's full path in UEFI
Date: Tue, 27 Sep 2016 11:51:54 +0000 [thread overview]
Message-ID: <CABKwMdvcm17r+36DjbD-v3JUBjwm1fLB_mwwqNMh-NZv3QiWww@mail.gmail.com> (raw)
In-Reply-To: <87d54199-6065-47e4-b3f8-04fd6f93220f@redhat.com>
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
> > >
> >
>
>
next prev parent reply other threads:[~2016-09-27 11:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 9:03 How to open a file by it's full path in UEFI GN Keshava
2016-09-27 9:07 ` Andrew Fish
2016-09-27 9:28 ` GN Keshava
2016-09-27 9:16 ` Laszlo Ersek
2016-09-27 9:25 ` GN Keshava
2016-09-27 9:49 ` Laszlo Ersek
2016-09-27 10:46 ` GN Keshava
2016-09-27 11:17 ` Laszlo Ersek
2016-09-27 11:51 ` GN Keshava [this message]
2016-09-27 15:07 ` Carsey, Jaben
2016-09-27 15:13 ` Laszlo Ersek
2016-09-27 16:44 ` Jarlstrom, Laurie
2016-09-27 16:48 ` Andrew Fish
2016-09-27 16:56 ` GN Keshava
2016-09-29 10:22 ` GN Keshava
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