From: ymdatta <ymdatta.work@gmail.com>
To: Greg KH <greg@kroah.com>
Cc: kernelnewbies@kernelnewbies.org
Subject: Re: Accessing allocated space in a debugfs file
Date: Fri, 2 Oct 2020 16:59:24 +0530 [thread overview]
Message-ID: <1e7b7d6d-0764-01fc-e527-f2e703e45ca2@gmail.com> (raw)
In-Reply-To: <20200930174906.GA1687038@kroah.com>
On 30/09/20 11:19 pm, Greg KH wrote:
> On Wed, Sep 30, 2020 at 10:32:05PM +0530, ymdatta wrote:
>>
>> I want to write in this file, how should i be accessing the space created
>> from previous function call.
>
> That's not what "size" means here. "size" just sets the value that you
> see if you look at the directory for that debugfs file (or stat() it).
>
Didn't realize this. Why do we need this then? What does this 'size' help
in achieving (or) where is this used?
> debugfs is a virtual filesystem, there is no "backing store" or place to
> put your data in it. It is there so that you can write code that can
> handle open/read/write/close to happen on a file, and your code will
> provide the data to userspace directly.
>
> The simplest way to create a debugfs file is to just point it at a
> variable, and then you can change the variable value in the kernel, and
> userspace reading from the file will see whatever the value is at that
> point in time.
This clears up a lot of my doubts. Thanks!
ymdatta.
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next prev parent reply other threads:[~2020-10-02 11:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 17:02 Accessing allocated space in a debugfs file ymdatta
2020-09-30 17:49 ` Greg KH
2020-10-02 11:29 ` ymdatta [this message]
2020-10-02 11:35 ` Greg KH
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