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Date: Thu, 18 Sep 2014 15:22:33 -0500 From: Kim Phillips <kim.phillips@...escale.com> To: Alexander Graf <agraf@...e.de> CC: German Rivera <German.Rivera@...escale.com>, "<gregkh@...uxfoundation.org>" <gregkh@...uxfoundation.org>, "<arnd@...db.de>" <arnd@...db.de>, "<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>, "<stuart.yoder@...escale.com>" <stuart.yoder@...escale.com>, "<scottwood@...escale.com>" <scottwood@...escale.com>, "<linuxppc-release@...ux.freescale.net>" <linuxppc-release@...ux.freescale.net> Subject: Re: [PATCH 1/4] drivers/bus: Added Freescale Management Complex APIs On Thu, 18 Sep 2014 15:14:03 +0200 Alexander Graf <agraf@...e.de> wrote: > > Am 18.09.2014 um 06:17 schrieb German Rivera <German.Rivera@...escale.com>: > > > >> On 09/15/2014 06:44 PM, Kim Phillips wrote: > >> On Thu, 11 Sep 2014 12:34:21 -0500 > >> "J. German Rivera" <German.Rivera@...escale.com> wrote: > >> > >>> From: "J. German Rivera" <German.Rivera@...escale.com> > >>> > >>> APIs to access the Management Complex (MC) hardware > >>> module of Freescale LS2 SoCs. This patch includes > >>> APIs to check the MC firmware version and to manipulate > >>> DPRC objects in the MC. > >>> > >>> Signed-off-by: J. German Rivera <German.Rivera@...escale.com> > >>> Signed-off-by: Stuart Yoder <stuart.yoder@...escale.com> > >>> --- > >>> drivers/bus/fsl-mc/dpmng.c | 93 +++++ > >>> drivers/bus/fsl-mc/dprc.c | 504 +++++++++++++++++++++++ > >>> drivers/bus/fsl-mc/fsl_dpmng_cmd.h | 83 ++++ > >>> drivers/bus/fsl-mc/fsl_dprc_cmd.h | 545 +++++++++++++++++++++++++ > >>> drivers/bus/fsl-mc/fsl_mc_sys.c | 237 +++++++++++ > >>> include/linux/fsl_dpmng.h | 120 ++++++ > >>> include/linux/fsl_dprc.h | 790 ++++++++++++++++++++++++++++++++++++ > >>> include/linux/fsl_mc_cmd.h | 182 +++++++++ > >>> include/linux/fsl_mc_sys.h | 81 ++++ > >>> 9 files changed, 2635 insertions(+) > >>> create mode 100644 drivers/bus/fsl-mc/dpmng.c > >>> create mode 100644 drivers/bus/fsl-mc/dprc.c > >>> create mode 100644 drivers/bus/fsl-mc/fsl_dpmng_cmd.h > >>> create mode 100644 drivers/bus/fsl-mc/fsl_dprc_cmd.h > >>> create mode 100644 drivers/bus/fsl-mc/fsl_mc_sys.c > >>> create mode 100644 include/linux/fsl_dpmng.h > >>> create mode 100644 include/linux/fsl_dprc.h > >>> create mode 100644 include/linux/fsl_mc_cmd.h > >>> create mode 100644 include/linux/fsl_mc_sys.h > >> > >> the fsl prefix in the filename fsl_dpmng_cmd.h is redundant with > >> its directory name fsl-mc/. Note that I find dashes ('-') in > >> filenames make them easier to type: is there a reason we're using > >> underscores here? > > This is a convention that we decided early on '-' for directory names > > and '_' for file names. based on what? > > unnecessarily complicated error path, plus a simpler > >> implementation can be made if fn can return the mapped address, like > >> so: > >> > >> static void __iomem *map_mc_portal(phys_addr_t mc_portal_phys_addr, > >> uint32_t mc_portal_size) > >> { > >> struct resource *res; > >> void __iomem *mapped_addr; > >> > >> res = request_mem_region(mc_portal_phys_addr, mc_portal_size, > >> "mc_portal"); > >> if (!res) > >> return NULL; > >> > >> mapped_addr = ioremap_nocache(mc_portal_phys_addr, > >> mc_portal_size); > >> if (!mapped_addr) > >> release_mem_region(mc_portal_phys_addr, mc_portal_size); > >> > >> return mapped_addr; > >> } > >> > >> the callsite can return -ENOMEM to its caller if returned NULL. This > >> can be improved even further if devm_ functions are used: this is > >> just an example of how to simplify the code using early returns > >> instead of goto error. > > > > I disagree. Having a common error return point is more maintainable than having multiple returns as having the clean-up logic in one place is more maintainable and makes the min path (non-error) more readable. my comment is not that much different from Joe's here: https://lkml.org/lkml/2014/9/17/381 but hopefully all this will change with a devm_ based implementation. > >>> +int __must_check fsl_create_mc_io(phys_addr_t mc_portal_phys_addr, > >>> + uint32_t mc_portal_size, > >>> + uint32_t flags, struct fsl_mc_io **new_mc_io) > >>> +{ > >>> + int error = -EINVAL; > >>> + struct fsl_mc_io *mc_io = NULL; > >>> + > >>> + mc_io = kzalloc(sizeof(*mc_io), GFP_KERNEL); > >>> + if (mc_io == NULL) { > >>> + error = -ENOMEM; > >>> + pr_err("No memory to allocate mc_io\n"); > >>> + goto error; > >>> + } > >>> + > >>> + mc_io->magic = FSL_MC_IO_MAGIC; > >>> + mc_io->flags = flags; > >>> + mc_io->portal_phys_addr = mc_portal_phys_addr; > >>> + mc_io->portal_size = mc_portal_size; > >>> + spin_lock_init(&mc_io->spinlock); > >>> + error = map_mc_portal(mc_portal_phys_addr, > >>> + mc_portal_size, &mc_io->portal_virt_addr); > >>> + if (error < 0) > >>> + goto error; > >>> + > >>> + *new_mc_io = mc_io; > >>> + return 0; > >> > >> if a fn only returns an address or error, it can return ERR_PTR > >> (e.g., -ENOMEM), and the callsite use IS_ERR() to determine whether > >> there was an error or address returned. This makes code much > >> simpler instead of passing address values back by reference. > > I disagree. I don't see why the alternative you suggest makes the code "much simpler". because it eliminates the need for the extra pass-by-reference argument struct fsl_mc_io **new_mc_io. > >>> +void fsl_destroy_mc_io(struct fsl_mc_io *mc_io) > >>> +{ > >>> + if (WARN_ON(mc_io->magic != FSL_MC_IO_MAGIC)) > >>> + return; > >>> + > >>> + if (mc_io->portal_virt_addr != NULL) { > >>> + unmap_mc_portal(mc_io->portal_phys_addr, > >>> + mc_io->portal_size, mc_io->portal_virt_addr); > >> > >> unmap_mc_portal already checks for virt_addr, this is another > >> example where the code goes too far checking for NULL. > > I disagree. Having the extra check is harmless and more importantly makes the intent explicit that we should only call unmap_mc_portal if we called map_mc_portal earlier. the code is doing this: if (mc_io->portal_virt_addr != NULL) { if (WARN_ON(mc_portal_virt_addr == NULL)) return; which is redundant and therefore makes it unnecessarily complicated, after all, a stack trace will occur if mc_portal_virt_addr is referenced anyway, making the WARN_ON clause redundant, too. > >>> + mc_io->portal_virt_addr = NULL; > >>> + } > >>> + > >>> + mc_io->magic = 0x0; > >>> + kfree(mc_io); > >>> +} btw, what's the point of zeroing out things that are being freed? > >>> +/** > >>> + * @brief Management Complex firmware version information > >>> + */ > >>> +#define MC_VER_MAJOR 2 > >>> +#define MC_VER_MINOR 0 > >> > >> code should be adjusted to run on all *compatible* versions of h/w, > >> not strictly the one set in these defines. > > This comment is not precise enough be actionable. > > What exactly you want to be changed here? > > I think the easy thing to do is to convert the exact version check into a ranged version check: have minimum and maximum versions you support. Or a list of exact versions you support. Or not check for the version at all - or only for the major version and guarantee that the major version indicates backwards compatibility. yes, this was my point: elsewhere I noticed the code denies to run iff those defines are not matched exactly: that code should change to run as Alex describes. > >>> +/** > >>> + * @brief Disconnects one endpoint to remove its network link > >>> + * > >>> + * @param[in] mc_io Pointer to opaque I/O object > >>> + * @param[in] dprc_handle Handle to the DPRC object > >>> + * @param[in] endpoint Endpoint configuration parameters. > >>> + * > >>> + * @returns '0' on Success; Error code otherwise. > >>> + * */ > >>> +int dprc_disconnect(struct fsl_mc_io *mc_io, uint16_t dprc_handle, > >>> + struct dprc_endpoint *endpoint); > >>> + > >>> +/*! @} */ > >> > >> this entire file is riddled with non-kernel-doc comment markers: see > >> Documentation/kernel-doc-nano-HOWTO.txt on how to write function and > >> other types of comments in a kernel-doc compliant format. > > This is because this file is using doxygen comments, as it was developed > > by another team. Unless someone else has an objection, I will leave the doxygen comments alone and not make any change here. > > Do you see any other source files in Linux using doxygen comments? Mixing different documentation styles can easily become a big mess, because you can't generate external documentation consistently for the whole tree. Thanks Alex, Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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