dfu: rename dfu_tftp_write() to dfu_write_by_name()

This function is essentially independent from tftp, and will also be
utilised in implementing UEFI capsule update in a later commit.
So just give it a more generic name.
In addition, a new configuration option, CONFIG_DFU_WRITE_ALT, was
introduced so that the file will be compiled with different options,
particularly one added in a later commit.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/dfu/dfu_alt.c b/drivers/dfu/dfu_alt.c
new file mode 100644
index 0000000..8870967
--- /dev/null
+++ b/drivers/dfu/dfu_alt.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2015
+ * Lukasz Majewski <l.majewski@majess.pl>
+ */
+
+#include <common.h>
+#include <log.h>
+#include <malloc.h>
+#include <errno.h>
+#include <dfu.h>
+
+/**
+ * dfu_write_by_name() - write data to DFU medium
+ * @dfu_entity_name:    Name of DFU entity to write
+ * @addr:               Address of data buffer to write
+ * @len:                Number of bytes
+ * @interface:          Destination DFU medium (e.g. "mmc")
+ * @devstring:          Instance number of destination DFU medium (e.g. "1")
+ *
+ * This function is storing data received on DFU supported medium which
+ * is specified by @dfu_entity_name.
+ *
+ * Return:              0 - on success, error code - otherwise
+ */
+int dfu_write_by_name(char *dfu_entity_name, unsigned int addr,
+		      unsigned int len, char *interface, char *devstring)
+{
+	char *s, *sb;
+	int alt_setting_num, ret;
+	struct dfu_entity *dfu;
+
+	debug("%s: name: %s addr: 0x%x len: %d device: %s:%s\n", __func__,
+	      dfu_entity_name, addr, len, interface, devstring);
+
+	ret = dfu_init_env_entities(interface, devstring);
+	if (ret)
+		goto done;
+
+	/*
+	 * We need to copy name pointed by *dfu_entity_name since this text
+	 * is the integral part of the FDT image.
+	 * Any implicit modification (i.e. done by strsep()) will corrupt
+	 * the FDT image and prevent other images to be stored.
+	 */
+	s = strdup(dfu_entity_name);
+	sb = s;
+	if (!s) {
+		ret = -ENOMEM;
+		goto done;
+	}
+
+	strsep(&s, "@");
+	debug("%s: image name: %s strlen: %zd\n", __func__, sb, strlen(sb));
+
+	alt_setting_num = dfu_get_alt(sb);
+	free(sb);
+	if (alt_setting_num < 0) {
+		pr_err("Alt setting [%d] to write not found!",
+		       alt_setting_num);
+		ret = -ENODEV;
+		goto done;
+	}
+
+	dfu = dfu_get_entity(alt_setting_num);
+	if (!dfu) {
+		pr_err("DFU entity for alt: %d not found!", alt_setting_num);
+		ret = -ENODEV;
+		goto done;
+	}
+
+	ret = dfu_write_from_mem_addr(dfu, (void *)(uintptr_t)addr, len);
+
+done:
+	dfu_free_entities();
+
+	return ret;
+}