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Message-ID: <20190409032331.GA478@innovation.ch> Date: Mon, 8 Apr 2019 20:23:31 -0700 From: "Life is hard, and then you die" <ronald@...ovation.ch> To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, Henrik Rydberg <rydberg@...math.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Lukas Wunner <lukas@...ner.de>, Federico Lorenzi <federico@...velground.com>, linux-input@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 2/2] Input: add Apple SPI keyboard and trackpad driver. On Mon, Apr 08, 2019 at 03:33:43PM +0300, Andy Shevchenko wrote: > On Sat, Apr 06, 2019 at 10:03:58PM -0700, Ronald Tschalär wrote: > > The keyboard and trackpad on recent MacBook's (since 8,1) and > > MacBookPro's (13,* and 14,*) are attached to an SPI controller instead > > of USB, as previously. The higher level protocol is not publicly > > documented and hence has been reverse engineered. As a consequence there > > are still a number of unknown fields and commands. However, the known > > parts have been working well and received extensive testing and use. > > > > In order for this driver to work, the proper SPI drivers need to be > > loaded too; for MB8,1 these are spi_pxa2xx_platform and spi_pxa2xx_pci; > > for all others they are spi_pxa2xx_platform and intel_lpss_pci. For this > > reason enabling this driver in the config implies enabling the above > > drivers. > > Thank you for an update, my comments below. Thank you again for your review. [snip] > > + } else { > > + struct dentry *ret; > > + > > + ret = debugfs_create_bool("enable_tp_dim", 0600, > > + applespi->debugfs_root, > > + &applespi->debug_tp_dim); > > + if (IS_ERR(ret)) > > + dev_warn(&(applespi)->spi->dev, > > + "Error creating debugfs entry enable_tp_dim (%ld)\n", > > + PTR_ERR(ret)); > > Can ret be NULL? No, it actually can't (I manually traced all code paths to be sure): the documentation for these helper functions is wrong in this respect. However, I note that a lot of existing kernel code also has this wrong (i.e. it's checking for NULL). Digging a bit further and looking at the history, it appears this was changed just recently (commit ff9fb72b "debugfs: return error values, not NULL"), which would explain the existing code and documentation. I'll submit a patch to update the docs. > dev_dbg() looks more appropriate. Hmm, ok, I guess I find this a bit odd, though: true, this only affects code used for debugging, but it's nevertheless an error that shouldn't normally occur. Cheers, Ronald
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