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| author | Ulf Hansson <ulf.hansson@linaro.org> | 2021-02-12 16:16:10 +0300 |
|---|---|---|
| committer | Ulf Hansson <ulf.hansson@linaro.org> | 2021-03-30 12:41:58 +0300 |
| commit | e9ce2ce17da626d930812199568bd426b2832f57 (patch) | |
| tree | 060463a56d8f9f649ea9f45a66714bd59beccc37 /include/linux/mmc | |
| parent | fefdd3c91e0a7b3cbb3f25925d93a57c45cb0f31 (diff) | |
| download | linux-e9ce2ce17da626d930812199568bd426b2832f57.tar.xz | |
mmc: core: Drop reference counting of the bus_ops
When the mmc_rescan work is enabled for execution (host->rescan_disable),
it's the only instance per mmc host that is allowed to set/clear the
host->bus_ops pointer.
Besides the mmc_rescan work, there are a couple of scenarios when the
host->bus_ops pointer may be accessed. Typically, those can be described as
as below:
*)
Upper mmc driver layers (like the mmc block device driver or an SDIO
functional driver) needs to execute a host->bus_ops callback. This can be
considered as safe without having to use some special locking mechanism,
because they operate on top of the struct mmc_card. As long as there is a
card to operate upon, the mmc core guarantees that there is a host->bus_ops
assigned as well. Note that, upper layer mmc drivers are of course
responsible to clean up from themselves from their ->remove() callbacks,
otherwise things would fall apart anyways.
**)
Via the mmc host instance, we may need to force a removal of an inserted
mmc card. This happens when a mmc host driver gets unbind, for example. In
this case, we protect the host->bus_ops pointer from concurrent accesses,
by disabling the mmc_rescan work upfront (host->rescan_disable). See
mmc_stop_host() for example.
This said, it seems like the reference counting of the host->bus_ops
pointer at some point have become superfluous. As this is an old mechanism
of the mmc core, it a bit difficult to digest the history of when that
could have happened. However, let's drop the reference counting to avoid
unnecessary code-paths and lockings.
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20210212131610.236843-1-ulf.hansson@linaro.org
Diffstat (limited to 'include/linux/mmc')
| -rw-r--r-- | include/linux/mmc/host.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index 26a3c7bc29ae..a001ad2f5f23 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -423,7 +423,6 @@ struct mmc_host { /* group bitfields together to minimize padding */ unsigned int use_spi_crc:1; unsigned int claimed:1; /* host exclusively claimed */ - unsigned int bus_dead:1; /* bus has been released */ unsigned int doing_init_tune:1; /* initial tuning in progress */ unsigned int can_retune:1; /* re-tuning can be used */ unsigned int doing_retune:1; /* re-tuning in progress */ @@ -454,7 +453,6 @@ struct mmc_host { struct mmc_slot slot; const struct mmc_bus_ops *bus_ops; /* current bus driver */ - unsigned int bus_refs; /* reference counter */ unsigned int sdio_irqs; struct task_struct *sdio_irq_thread; |