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Piccoli" , Florian Fainelli , Arend van Spriel , William Zhang , bcm-kernel-feedback-list@broadcom.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Kamal Dasu Subject: [PATCH v4 3/4] mmc: block: Add helper to look up mmc_card by device name Date: Fri, 20 Mar 2026 16:32:48 -0400 Message-Id: <20260320203249.1965044-4-kamal.dasu@broadcom.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260320203249.1965044-1-kamal.dasu@broadcom.com> References: <20260320203249.1965044-1-kamal.dasu@broadcom.com> Precedence: bulk X-Mailing-List: linux-mmc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e Add mmc_blk_get_card_by_name() which resolves an MMC block device name (e.g., "mmcblk1") to its associated struct mmc_card by opening the block device and traversing gendisk to the mmc_blk_data private data. This is needed by the mmcpstore backend driver to find the card associated with a given pstore_blk block device path. When mmcpstore is built as a module, the eMMC card is already probed by the time the module loads, so the helper can look it up directly. Signed-off-by: Kamal Dasu --- drivers/mmc/core/block.c | 54 ++++++++++++++++++++++++++++++++++++++++ drivers/mmc/core/block.h | 4 +++ 2 files changed, 58 insertions(+) diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index 05ee76cb0a08..91e3a778d5b2 100644 --- a/drivers/mmc/core/block.c +++ b/drivers/mmc/core/block.c @@ -3441,6 +3441,60 @@ static void __exit mmc_blk_exit(void) bus_unregister(&mmc_rpmb_bus_type); } +/** + * mmc_blk_get_card_by_name - Get mmc_card from device name + * @device_name: Name of the MMC device (e.g., "mmcblk1") + * + * Resolves an MMC block device name to its associated struct mmc_card. + * Used by the mmcpstore backend driver (when built as a module) to find + * the card associated with a given pstore_blk block device path. + * + * Returns: mmc_card pointer on success, NULL on failure + */ +struct mmc_card *mmc_blk_get_card_by_name(const char *device_name) +{ + struct file *bdev_file; + struct block_device *bdev; + struct gendisk *disk; + struct mmc_blk_data *md; + struct mmc_card *card = NULL; + char dev_path[32]; + + if (!device_name) + return NULL; + + snprintf(dev_path, sizeof(dev_path), "/dev/%s", device_name); + + bdev_file = bdev_file_open_by_path(dev_path, BLK_OPEN_READ, NULL, NULL); + if (IS_ERR(bdev_file)) { + pr_debug("mmc_blk: Failed to open block device %s: %ld\n", + dev_path, PTR_ERR(bdev_file)); + return NULL; + } + bdev = file_bdev(bdev_file); + + disk = bdev->bd_disk; + if (!disk) { + pr_err("mmc_blk: No gendisk found for %s\n", dev_path); + goto out_put_bdev; + } + + md = disk->private_data; + if (!md) { + pr_debug("mmc_blk: No mmc_blk_data found for %s\n", dev_path); + goto out_put_bdev; + } + + card = md->queue.card; + if (!card) + pr_err("mmc_blk: No mmc_card found for %s\n", dev_path); + +out_put_bdev: + fput(bdev_file); + return card; +} +EXPORT_SYMBOL_GPL(mmc_blk_get_card_by_name); + module_init(mmc_blk_init); module_exit(mmc_blk_exit); diff --git a/drivers/mmc/core/block.h b/drivers/mmc/core/block.h index 31153f656f41..08798c56dcce 100644 --- a/drivers/mmc/core/block.h +++ b/drivers/mmc/core/block.h @@ -17,4 +17,8 @@ struct work_struct; void mmc_blk_mq_complete_work(struct work_struct *work); +/* MMC block device helper for mmcpstore */ +struct mmc_card; +struct mmc_card *mmc_blk_get_card_by_name(const char *device_name); + #endif -- 2.34.1