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

From: Ekansh Gupta
Date: Fri Apr 11 2025 - 04:26:14 EST



On 12/3/2024 5:27 PM, Dmitry Baryshkov wrote:
> On Tue, 3 Dec 2024 at 07:22, Ekansh Gupta <quic_ekangupt@xxxxxxxxxxx> 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@xxxxxxxxxxx>
>>>>>>>> ---
>>>>>>>> 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.

Hi all,

I'm adding Deepika <quic_dsi@xxxxxxxxxxx> to this thread who is reworking
on this patch series.

//Ekansh

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