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    Subject[PATCH v3] cros_ec: cleanup dependency chain for cros_ec modules
    From
    From: Enrico Granata <egranata@chromium.org>

    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

    Series-to: LKML <linux-kernel@vger.kernel.org>
    Series-cc: gwendal@google.com
    Signed-off-by: Enrico Granata <egranata@chromium.org>
    ---
    drivers/mfd/Kconfig | 1 -
    drivers/mfd/Makefile | 2 +-
    drivers/mfd/cros_ec.c | 18 ++++++++++++++++--
    drivers/mfd/cros_ec_i2c.c | 1 +
    drivers/{platform/chrome => mfd}/cros_ec_proto.c | 0
    drivers/mfd/cros_ec_spi.c | 1 +
    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 ++
    10 files changed, 22 insertions(+), 10 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
    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..9660dc0fc079 100644
    --- a/drivers/mfd/cros_ec.c
    +++ b/drivers/mfd/cros_ec.c
    @@ -168,8 +168,19 @@ 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",
    - err);
    + dev_dbg(dev, "Error %d clearing sleep event to ec", err);
    +
    + 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");

    @@ -193,6 +204,9 @@ 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/mfd/cros_ec_i2c.c b/drivers/mfd/cros_ec_i2c.c
    index 9f70de1e4c70..72b0473eb868 100644
    --- a/drivers/mfd/cros_ec_i2c.c
    +++ b/drivers/mfd/cros_ec_i2c.c
    @@ -302,6 +302,7 @@ static int cros_ec_i2c_probe(struct i2c_client *client,
    ec_dev->irq = client->irq;
    ec_dev->cmd_xfer = cros_ec_cmd_xfer_i2c;
    ec_dev->pkt_xfer = cros_ec_pkt_xfer_i2c;
    + ec_dev->xfer_fcn_owner = THIS_MODULE;
    ec_dev->phys_name = client->adapter->name;
    ec_dev->din_size = sizeof(struct ec_host_response_i2c) +
    sizeof(struct ec_response_get_protocol_info);
    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/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
    index 2060d1483043..ce2849790b95 100644
    --- a/drivers/mfd/cros_ec_spi.c
    +++ b/drivers/mfd/cros_ec_spi.c
    @@ -666,6 +666,7 @@ static int cros_ec_spi_probe(struct spi_device *spi)
    ec_dev->irq = spi->irq;
    ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
    ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
    + ec_dev->xfer_fcn_owner = THIS_MODULE;
    ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
    ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
    sizeof(struct ec_host_response) +
    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;
    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;
    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
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