firmware: consolidate kmap/read/write logic (9ccf9811) · Commits · 戴 / test

Some systems are memory constrained but they need to load very large firmwares. The firmware subsystem allows drivers to request this firmware be loaded from the filesystem, but this requires that the entire firmware be loaded into kernel memory first before it's provided to the driver. This can lead to a situation where we map the firmware twice, once to load the firmware into kernel memory and once to copy the firmware into the final resting place. This design creates needless memory pressure and delays loading because we have to copy from kernel memory to somewhere else. This patch sets adds support to the request firmware API to load the firmware directly into a pre-allocated buffer, skipping the intermediate copying step and alleviating memory pressure during firmware loading. The drawback is that we can't use the firmware caching feature because the memory for the firmware cache is not managed by the firmware layer. This patch (of 3): We use similar structured code to read and write the kmapped firmware pages. The only difference is read copies from the kmap region and write copies to it. Consolidate this into one function to reduce duplication. Link: http://lkml.kernel.org/r/20160607164741.31849-2-stephen.boyd@linaro.org Signed-off-by:

Stephen Boyd <stephen.boyd@linaro.org> Cc: Vikram Mulukutla <markivx@codeaurora.org> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> Cc: Mark Brown <broonie@kernel.org> Cc: Ming Lei <ming.lei@canonical.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/firmware_class.c

+26 −31

Original line number	Diff line number	Diff line
		@@ -691,6 +691,29 @@ out:

		static DEVICE_ATTR(loading, 0644, firmware_loading_show, firmware_loading_store);

		static void firmware_rw(struct firmware_buf buf, char buffer,
		loff_t offset, size_t count, bool read)
		{
		while (count) {
		void *page_data;
		int page_nr = offset >> PAGE_SHIFT;
		int page_ofs = offset & (PAGE_SIZE-1);
		int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count);

		page_data = kmap(buf->pages[page_nr]);

		if (read)
		memcpy(buffer, page_data + page_ofs, page_cnt);
		else
		memcpy(page_data + page_ofs, buffer, page_cnt);

		kunmap(buf->pages[page_nr]);
		buffer += page_cnt;
		offset += page_cnt;
		count -= page_cnt;
		}
		}

		static ssize_t firmware_data_read(struct file filp, struct kobject kobj,
		struct bin_attribute *bin_attr,
		char *buffer, loff_t offset, size_t count)
		@@ -715,21 +738,8 @@ static ssize_t firmware_data_read(struct file filp, struct kobject kobj,

		ret_count = count;

		while (count) {
		void *page_data;
		int page_nr = offset >> PAGE_SHIFT;
		int page_ofs = offset & (PAGE_SIZE-1);
		int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count);

		page_data = kmap(buf->pages[page_nr]);

		memcpy(buffer, page_data + page_ofs, page_cnt);
		firmware_rw(buf, buffer, offset, count, true);

		kunmap(buf->pages[page_nr]);
		buffer += page_cnt;
		offset += page_cnt;
		count -= page_cnt;
		}
		out:
		mutex_unlock(&fw_lock);
		return ret_count;
		@@ -809,24 +819,9 @@ static ssize_t firmware_data_write(struct file filp, struct kobject kobj,
		goto out;

		retval = count;
		firmware_rw(buf, buffer, offset, count, false);

		while (count) {
		void *page_data;
		int page_nr = offset >> PAGE_SHIFT;
		int page_ofs = offset & (PAGE_SIZE - 1);
		int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count);

		page_data = kmap(buf->pages[page_nr]);

		memcpy(page_data + page_ofs, buffer, page_cnt);

		kunmap(buf->pages[page_nr]);
		buffer += page_cnt;
		offset += page_cnt;
		count -= page_cnt;
		}

		buf->size = max_t(size_t, offset, buf->size);
		buf->size = max_t(size_t, offset + count, buf->size);
		out:
		mutex_unlock(&fw_lock);
		return retval;

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