linux-kernel - Re: LDD 3rd ed. - It was: Re: read() via USB bus

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Message-ID: <61d7271d-d3cb-f25d-eaad-5489461a3bef@crashcourse.ca>
Date:   Thu, 12 Aug 2021 06:26:44 -0400 (EDT)
From:   "Robert P. J. Day" <rpjday@...shcourse.ca>
To:     Greg KH <gregkh@...uxfoundation.org>
cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Muni Sekhar <munisekharrms@...il.com>,
        Oliver Neukum <oneukum@...e.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        kernelnewbies <kernelnewbies@...nelnewbies.org>
Subject: Re: LDD 3rd ed. - It was: Re: read() via USB bus

On Thu, 12 Aug 2021, Greg KH wrote:

> On Thu, Aug 12, 2021 at 11:45:45AM +0200, Fabio M. De Francesco wrote:
> > 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.
>
> Look into it and see the differences, it's not hard to notice.
>
> And the code samples are all up to date online on github somewhere,
> there's people keeping them alive if you want to track them down,
> but really, just look at the in-kernel drivers for better examples
> of real drivers.

  it's possibly worth mentioning that a chap named javier martinez has
been doing a decent job of upgrading the examples from LDD3 to keep up
with current kernel development:

  https://github.com/martinezjavier/ldd3

of course, those examples won't match the explanations in the book
anymore, but still, worth perusing.

rday