[PATCH v1 4/4] misc: fastrpc: Add debugfs support for fastrpc

[Dmitry Baryshkov]

On Tue, 3 Dec 2024 at 07:22, Ekansh Gupta <quic_ekangupt at quicinc.com> wrote:
>
>
>
> On 12/2/2024 6:18 PM, Dmitry Baryshkov wrote:
> > On Mon, Dec 02, 2024 at 03:27:43PM +0530, Ekansh Gupta wrote:
> >>
> >> On 11/22/2024 12:23 AM, Dmitry Baryshkov wrote:
> >>> On Thu, Nov 21, 2024 at 12:12:17PM +0530, Ekansh Gupta wrote:
> >>>> On 11/18/2024 7:32 PM, Greg KH wrote:
> >>>>> On Mon, Nov 18, 2024 at 02:10:46PM +0530, Ekansh Gupta wrote:
> >>>>>> Add changes to support debugfs. The fastrpc directory will be
> >>>>>> created which will carry debugfs files for all fastrpc processes.
> >>>>>> The information of fastrpc user and channel contexts are getting
> >>>>>> captured as part of this change.
> >>>>>>
> >>>>>> Signed-off-by: Ekansh Gupta <quic_ekangupt at quicinc.com>
> >>>>>> ---
> >>>>>>  drivers/misc/fastrpc/Makefile        |   3 +-
> >>>>>>  drivers/misc/fastrpc/fastrpc_debug.c | 156 +++++++++++++++++++++++++++
> >>>>>>  drivers/misc/fastrpc/fastrpc_debug.h |  31 ++++++
> >>>>>>  drivers/misc/fastrpc/fastrpc_main.c  |  18 +++-
> >>>>>>  4 files changed, 205 insertions(+), 3 deletions(-)
> >>>>>>  create mode 100644 drivers/misc/fastrpc/fastrpc_debug.c
> >>>>>>  create mode 100644 drivers/misc/fastrpc/fastrpc_debug.h
> >>>>>>
> >>>>>> diff --git a/drivers/misc/fastrpc/Makefile b/drivers/misc/fastrpc/Makefile
> >>>>>> index 020d30789a80..4ff6b64166ae 100644
> >>>>>> --- a/drivers/misc/fastrpc/Makefile
> >>>>>> +++ b/drivers/misc/fastrpc/Makefile
> >>>>>> @@ -1,3 +1,4 @@
> >>>>>>  # SPDX-License-Identifier: GPL-2.0
> >>>>>>  obj-$(CONFIG_QCOM_FASTRPC)      += fastrpc.o
> >>>>>> -fastrpc-objs    := fastrpc_main.o
> >>>>>> \ No newline at end of file
> >>>>>> +fastrpc-objs    := fastrpc_main.o \
> >>>>>> +                fastrpc_debug.o
> >>>>> Only build this file if debugfs is enabled.
> >>>>>
> >>>>> And again, "debug.c"?
> >>>> I'll add change to build this only if debugfs is enabled. Going forward I have plans to add
> >>>> few more debug specific changes, maybe then I'll need to change the build rules again.
> >>>>>> diff --git a/drivers/misc/fastrpc/fastrpc_debug.c b/drivers/misc/fastrpc/fastrpc_debug.c
> >>>>>> new file mode 100644
> >>>>>> index 000000000000..cdb4fc6845a8
> >>>>>> --- /dev/null
> >>>>>> +++ b/drivers/misc/fastrpc/fastrpc_debug.c
> >>>>>> @@ -0,0 +1,156 @@
> >>>>>> +// SPDX-License-Identifier: GPL-2.0
> >>>>>> +// Copyright (c) 2024 Qualcomm Innovation Center.
> >>>>>> +
> >>>>>> +#include <linux/debugfs.h>
> >>>>>> +#include <linux/seq_file.h>
> >>>>>> +#include "fastrpc_shared.h"
> >>>>>> +#include "fastrpc_debug.h"
> >>>>>> +
> >>>>>> +#ifdef CONFIG_DEBUG_FS
> >>>>> Please put the #ifdef in the .h file, not in the .c file.
> >>>> Ack
> >>>>>> +void fastrpc_create_user_debugfs(struct fastrpc_user *fl)
> >>>>>> +{
> >>>>>> +        char cur_comm[TASK_COMM_LEN];
> >>>>>> +        int domain_id, size;
> >>>>>> +        char *debugfs_buf;
> >>>>>> +        struct dentry *debugfs_dir = fl->cctx->debugfs_dir;
> >>>>>> +
> >>>>>> +        memcpy(cur_comm, current->comm, TASK_COMM_LEN);
> >>>>>> +        cur_comm[TASK_COMM_LEN-1] = '\0';
> >>>>>> +        if (debugfs_dir != NULL) {
> >>>>>> +                domain_id = fl->cctx->domain_id;
> >>>>>> +                size = snprintf(NULL, 0, "%.10s_%d_%d_%d", cur_comm,
> >>>>>> +                                current->pid, fl->tgid, domain_id) + 1;
> >>>>>> +                debugfs_buf = kzalloc(size, GFP_KERNEL);
> >>>>>> +                if (debugfs_buf == NULL)
> >>>>>> +                        return;
> >>>>>> +                /*
> >>>>>> +                 * Use HLOS process name, HLOS PID, fastrpc user TGID,
> >>>>>> +                 * domain_id in debugfs filename to create unique file name
> >>>>>> +                 */
> >>>>>> +                snprintf(debugfs_buf, size, "%.10s_%d_%d_%d",
> >>>>>> +                        cur_comm, current->pid, fl->tgid, domain_id);
> >>>>>> +                fl->debugfs_file = debugfs_create_file(debugfs_buf, 0644,
> >>>>>> +                                debugfs_dir, fl, &fastrpc_debugfs_fops);
> >>>>> Why are you saving the debugfs file?  What do you need to do with it
> >>>>> that you can't just delete the whole directory, or look up the name
> >>>>> again in the future when removing it?
> >>>> fl structure is specific to a process using fastrpc driver. The reason to save
> >>>> this debugfs file is to delete is when the process releases fastrpc device.
> >>>> If the file is not deleted, it might flood multiple files in debugfs directory.
> >>>>
> >>>> As part of this change, only the file that is getting created by a process is
> >>>> getting removed when process is releasing device and I don't think we
> >>>> can clean up the whole directory at this point.
> >>> My 2c: it might be better to create a single file that conains
> >>> information for all the processes instead of that. Or use fdinfo data to
> >>> export process / FD information to userspace.
> >> Thanks for your review. The reason of not having single file for all processes is that
> >> I can run 100s of iteration for any process(say calculator) and every time the properties
> >> of the process can differ(like buffer, session etc.). For this reason, I'm creating and
> >> deleting the debugfs files for every process run.
> >>
> >> Do you see any advantage of using fdinfo over debugfs? I'm not sure if we can add all
> >> the information(like in debugfs) here.
> > Which information is actually useful / interesting for application
> > developers? If not for the fdinfo, I might still vote for a single file
> > rather than a pile of per-process data.
> I have tried to capture all the information that could be useful.
>
> I can try changes to maintain single file for all active processes. Having this file specific
> to a channel should be fine, right? like fastrpc_adsp, fastrpc_cdsp, etc.? Each file will
> carry information of all processes using that remoteproc.

I think it's a better idea, yes.

>
> --ekansh
> >
> >> --ekansh
> >>>
>


-- 
With best wishes
Dmitry