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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Muni Sekhar <munisekharrms@gmail.com>,
        Oliver Neukum <oneukum@suse.com>,
        kernelnewbies <kernelnewbies@kernelnewbies.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: LDD 3rd ed. - It was: Re: read() via USB bus
Date:   Thu, 12 Aug 2021 11:45:45 +0200
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In-Reply-To: <YRDq530N/9uu2J0x@kroah.com>
References: <CAHhAz+jKREfXERKj7XB7U3Wh1g4STO2Dt0qnMkcPV5nXB3_bwg@mail.gmail.com> <8923f2b8-0be0-ffbf-70a4-c03c9a02d58a@suse.com> <YRDq530N/9uu2J0x@kroah.com>
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Hi Greg,

On Monday, August 9, 2021 10:44:23 AM CEST Greg KH wrote:
> On Mon, Aug 09, 2021 at 10:15:29AM +0200, Oliver Neukum wrote:
> > On 09.08.21 09:58, Muni Sekhar wrote:
> > > Hi all,
> > > 
> > > PCIe memory mapped registers can be read via readb(), readw(), readl()
> > > kernel API's. Similarly what are the kernel API to read the device
> > > registers via USB bus
> > 
> > [...]
> >
> > I hope this list stays friendly to newcomers and we will answer
> > specific questions, but at this point I must advise you to first
> > read an introductory book.
> 
> Along these lines, take a look at the book, Linux Device Drivers, third
> edition, which is free online, as it has a chapter about USB drivers and
> how they work.  That should help you out to understand the issues
> involved with USB devices.
> 
I've heard that your book, LDD 3rd edition, has become obsolete a long time 
ago and most sample code cannot anymore build. Reading what you wrote above 
seems to contradict what I've been told by others... I must admit that I've 
just had a print copy of it that I have not yet opened for reading, therefore 
maybe that I'm totally wrong in assuming the above.

Do you mind to elaborate a bit more on this subject, please? I mean: can you 
point out which chapters, which content, should be skipped (if there's really 
something which is no more correct/relevant to today's practice of drivers  
development and kernel hacking?

One more question, please... if after carefully studying its content, someone 
wanted to change and update part of the book content to reflect the changes in 
Linux API and in the current best practices, would it be (legally) allowed to 
publish a v4 on GitHub for the convenience of everyone interested in learning 
for free? However, I understand that it would be not so easy to come up with a 
good and error free text if not addressed as a public long term project and 
I'm also not sure of what tools are needed to edit PDF files. (At the moment 
my question is for a hypothetical scenario, just to know whether or not it 
would be technically and legally doable). 

I suppose that the answers to the above questions might be of interest to a 
lot of newcomers like me, so please, if you have time, I'd appreciate to read 
your reply.

Thanks,

Fabio
>
> If you have specific questions after looking at that, and reading the
> basic usb-skeleton.c driver in the kernel source tree, please let us
> know!
> 
> thanks,
> 
> greg k-h