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SubjectRe: [PATCH 3/3] usb: gadget: mass_storage: add documentation
> On Mon, 11 Jun 2012, Michal Nazarewicz wrote:
>> + Mass Storage Gadget (or MSG) acts as a USB Mass Storage device,
>> + appearing to the host as a disk or a CD-ROM drive. It supports
>> + multiple logical units (LUNs). Backing storage for each LUN is
>> + provided by a regular file or a block device, access can be limited
>> + to read-only, and gadget can indicate that it is removable and/or
>> + CD-ROM (the latter implies read-only access).

On Mon, 11 Jun 2012 17:25:15 +0200, Alan Stern <> wrote:
> Does CD-ROM really imply read-only? If not, shouldn't it?

It indeed does:

curlun->ro = lcfg->cdrom || lcfg->ro;
>> + - ro=b[,b...]
>> +
>> + This parameter specifies whether each logical unit should be
>> + reported as read only. This will prevent host from modifying the
>> + backing files.
>> +
>> + Note that if this flag for given logical unit is false but the
>> + backing file could not be opened in read/write mode, the gadget
>> + will fall back to read only mode anyway.
>> +
>> + The default value for each logical unit is false.
> Shouldn't the default be true for logical units that are cdroms?

Indeed. I've changed this last line to: The default value for non-CD-ROM
logical units is false; for logical units simulating CD-ROM it is forced
to true.

> Very good. When you make the small changes listed above, you can add
> Acked-by: Alan Stern <>

I'll resend it tomorrow in case anyone else has any comments.

Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp:>--------------ooO--(_)--Ooo--
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