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Subject: Re: What populates /proc/partitions ?
To:     "David F." <df7729@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <CAGRSmLsV96jK+7UB6T6k8j9u74oPSHTA+1TPU8F9G2NnOqCDJg@mail.gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <c0d9d434-1f47-66a0-1129-5003f2f2eb5c@infradead.org>
Date:   Mon, 30 Sep 2019 16:49:48 -0700
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On 9/30/19 3:47 PM, David F. wrote:
> Hi,
> 
> I want to find out why fd0 is being added to /proc/partitions and stop
> that for my build.  I've searched "/proc/partitions" and "partitions",
> not finding anything that matters.

/proc/partitions is produced on demand by causing a read of it.
That is done by these functions (pointers) in block/genhd.c:

static const struct seq_operations partitions_op = {
	.start	= show_partition_start,
	.next	= disk_seqf_next,
	.stop	= disk_seqf_stop,
	.show	= show_partition
};

in particular, show_partition().  In turn, that function uses data that was
produced upon block device discovery, also in block/genhd.c.
See functions disk_get_part(), disk_part_iter_init(), disk_part_iter_next(),
disk_part_iter_exit(), __device_add_disk(), and get_gendisk().

> If udev is doing it, what function is it call so I can search on that?

I don't know about that.  I guess in the kernel it is about "uevents".
E.g., in block/genhd.c, there are some calls to kobject_uevent() or variants
of it.

> TIA!!

There should be something in your boot log about "fd" or "fd0" or floppy.
eh?

-- 
~Randy