Re: [PATCH] Cleanup dependency chain for cros_ec modules

[Gwendal Grignou]

On Mon, Jun 4, 2018 at 1:22 PM Enrico Granata <egranata@xxxxxxxxxx> wrote:
>
> From: Enrico Granata <egranata@xxxxxxxxxxxx>
>
> If one builds the Chrome EC support as modules, there is no explicit
> dependency chain amongst the several modules (LPC, CHARDEV, CORE, ...)
>
> This makes it possible - for instance - to rmmod cros_ec_core, even though
> cros_ec_dev actively uses it for data transport to the EC chip.
>
> This commit makes two changes in an attempt to address this:
> a) moves cros_ec_proto.c as part of the CORE module; this removes the
>    possibility of unloading cros_ec_core while cros_ec_dev is using it;
> b) enables cros_ec_core to explicitly register a runtime dependency on
>    the kernel module that is using its cmd and pkt transfer functions
>
> Signed-off-by: Enrico Granata <egranata@xxxxxxxxxxxx>
> ---
>
>  drivers/mfd/Kconfig                             |  1 -
>  drivers/mfd/Makefile                            |  2 +-
>  drivers/mfd/cros_ec.c                           | 17 ++++++++++++++++-
>  .../{platform/chrome => mfd}/cros_ec_proto.c    |  0
>  drivers/platform/chrome/Kconfig                 |  5 -----
>  drivers/platform/chrome/Makefile                |  1 -
>  drivers/platform/chrome/cros_ec_lpc.c           |  1 +
>  include/linux/mfd/cros_ec.h                     |  2 ++
>  8 files changed, 20 insertions(+), 9 deletions(-)
>  rename drivers/{platform/chrome => mfd}/cros_ec_proto.c (100%)
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index b860eb5aa194..a8daa2072ae6 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -194,7 +194,6 @@ config MFD_CROS_EC
>         tristate "ChromeOS Embedded Controller"
>         select MFD_CORE
>         select CHROME_PLATFORMS
> -       select CROS_EC_PROTO
>         depends on X86 || ARM || ARM64 || COMPILE_TEST
>         help
>           If you say Y here you get support for the ChromeOS Embedded
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index d9d2cf0d32ef..20537bd27695 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -12,7 +12,7 @@ obj-$(CONFIG_MFD_SM501)               += sm501.o
>  obj-$(CONFIG_MFD_ASIC3)                += asic3.o tmio_core.o
>  obj-$(CONFIG_MFD_BCM590XX)     += bcm590xx.o
>  obj-$(CONFIG_MFD_BD9571MWV)    += bd9571mwv.o
> -cros_ec_core-objs              := cros_ec.o
> +cros_ec_core-objs              := cros_ec.o cros_ec_proto.o
We try to get cros_ec_proto out of mfd directory, it is weird to
compile something from drivers/platform/chrome/ in drivers/mfd.
>  cros_ec_core-$(CONFIG_ACPI)    += cros_ec_acpi_gpe.o
>  obj-$(CONFIG_MFD_CROS_EC)      += cros_ec_core.o
>  obj-$(CONFIG_MFD_CROS_EC_I2C)  += cros_ec_i2c.o
> diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
> index d61024141e2b..109e9cb1e289 100644
> --- a/drivers/mfd/cros_ec.c
> +++ b/drivers/mfd/cros_ec.c
> @@ -168,9 +168,21 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
>          */
>         err = cros_ec_sleep_event(ec_dev, 0);
>         if (err < 0)
> -               dev_dbg(ec_dev->dev, "Error %d clearing sleep event to ec",
> +               dev_dbg(dev, "Error %d clearing sleep event to ec",
>                         err);
Concatenate both line.
>
> +       if (ec_dev->xfer_fcn_owner != NULL) {
> +               err = try_module_get(ec_dev->xfer_fcn_owner);
> +               if (err < 0) {
> +                       dev_err(dev, "Error %d acquiring transfer module", err);
> +                       return err;
> +               }
> +               dev_info(dev, "Transfer module %p get successfully",
> +                        ec_dev->xfer_fcn_owner);
> +       } else {
> +               dev_warn(dev, "No transfer module registered");
> +       }
> +
>         dev_info(dev, "Chrome EC device registered\n");
>
>         cros_ec_acpi_install_gpe_handler(dev);
> @@ -193,6 +205,9 @@ int cros_ec_remove(struct cros_ec_device *ec_dev)
>         if (ec_dev->irq)
>                 free_irq(ec_dev->irq, ec_dev);
>
> +       if (ec_dev->xfer_fcn_owner != NULL)
> +               module_put(ec_dev->xfer_fcn_owner);
> +
>         return 0;
>  }
>  EXPORT_SYMBOL(cros_ec_remove);
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/mfd/cros_ec_proto.c
> similarity index 100%
> rename from drivers/platform/chrome/cros_ec_proto.c
> rename to drivers/mfd/cros_ec_proto.c
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index e728a96cabfd..a050c9e8b506 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -65,11 +65,6 @@ config CROS_EC_LPC_MEC
>           If you have a ChromeOS Embedded Controller Microchip EC variant
>           choose Y here.
>
> -config CROS_EC_PROTO
> -        bool
> -        help
> -          ChromeOS EC communication protocol helpers.
> -
>  config CROS_KBD_LED_BACKLIGHT
>         tristate "Backlight LED support for Chrome OS keyboards"
>         depends on LEDS_CLASS && ACPI
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index ff3b369911f0..0b5e26ca9c96 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -8,5 +8,4 @@ obj-$(CONFIG_CROS_EC_CTL)               += cros_ec_ctl.o
>  cros_ec_lpcs-objs                      := cros_ec_lpc.o cros_ec_lpc_reg.o
>  cros_ec_lpcs-$(CONFIG_CROS_EC_LPC_MEC) += cros_ec_lpc_mec.o
>  obj-$(CONFIG_CROS_EC_LPC)              += cros_ec_lpcs.o
> -obj-$(CONFIG_CROS_EC_PROTO)            += cros_ec_proto.o
>  obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)   += cros_kbd_led_backlight.o
> diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
> index 3682e1539251..8f02b188bd3f 100644
> --- a/drivers/platform/chrome/cros_ec_lpc.c
> +++ b/drivers/platform/chrome/cros_ec_lpc.c
> @@ -282,6 +282,7 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
>         ec_dev->phys_name = dev_name(dev);
>         ec_dev->cmd_xfer = cros_ec_cmd_xfer_lpc;
>         ec_dev->pkt_xfer = cros_ec_pkt_xfer_lpc;
> +       ec_dev->xfer_fcn_owner = THIS_MODULE;
You need to modify other transport modules as well:
cros_ec_i2c.c, cros_ec_spi.c.
>         ec_dev->cmd_readmem = cros_ec_lpc_readmem;
>         ec_dev->din_size = sizeof(struct ec_host_response) +
>                            sizeof(struct ec_response_get_protocol_info);
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index 2d4e23c9ea0a..5239107e5091 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -18,6 +18,7 @@
>
>  #include <linux/cdev.h>
>  #include <linux/device.h>
> +#include <linux/module.h>
>  #include <linux/notifier.h>
>  #include <linux/mfd/cros_ec_commands.h>
>  #include <linux/mutex.h>
> @@ -139,6 +140,7 @@ struct cros_ec_device {
>         int dout_size;
>         bool wake_enabled;
>         bool suspended;
> +       struct module *xfer_fcn_owner;
Another solution would be to make cros_ec a real module. lpc depends
on cros_ec_register, so lsmod will not unload cros_ec [core functions]
if cros_ec_lpc is still loaded.
>         int (*cmd_xfer)(struct cros_ec_device *ec,
>                         struct cros_ec_command *msg);
>         int (*pkt_xfer)(struct cros_ec_device *ec,
> --
> 2.17.1.1185.g55be947832-goog
>