[PATCH] PCI: endpoint: pci-epf-test: Allow overriding default BAR sizes

Niklas Cassel
2026-01-23T18:07:56Z

Add bar{0,1,2,3,4,5}_size attributes in configfs, so that the user is not
restricted to run pci-epf-test with the hardcoded BAR size values defined
in pci-epf-test.c.

This code is shamelessly more or less copy pasted from pci-epf-vntb.c

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
Documentation/PCI/endpoint/pci-test-howto.rst | 16 ++++
drivers/pci/endpoint/functions/pci-epf-test.c | 92 ++++++++++++++++++-
2 files changed, 106 insertions(+), 2 deletions(-)

diff --git a/Documentation/PCI/endpoint/pci-test-howto.rst b/Documentation/PCI/endpoint/pci-test-howto.rst
index dd66858cde46..71975721cfd5 100644
--- a/Documentation/PCI/endpoint/pci-test-howto.rst
+++ b/Documentation/PCI/endpoint/pci-test-howto.rst
@@ -84,6 +84,22 @@ device, the following commands can be used::
# echo 32 > functions/pci_epf_test/func1/msi_interrupts
# echo 2048 > functions/pci_epf_test/func1/msix_interrupts

+By default, pci-epf-test uses the following BAR sizes::
+
+ # grep . functions/pci_epf_test/func1/pci_epf_test.0/bar?_size
+ functions/pci_epf_test/func1/pci_epf_test.0/bar0_size:512
+ functions/pci_epf_test/func1/pci_epf_test.0/bar1_size:512
+ functions/pci_epf_test/func1/pci_epf_test.0/bar2_size:1024
+ functions/pci_epf_test/func1/pci_epf_test.0/bar3_size:16384
+ functions/pci_epf_test/func1/pci_epf_test.0/bar4_size:131072
+ functions/pci_epf_test/func1/pci_epf_test.0/bar5_size:1048576
+
+The user can override a default value using e.g.::
+ # echo 1048576 > functions/pci_epf_test/func1/pci_epf_test.0/bar1_size
+
+Note: Some endpoint controllers might have fixed size BARs, or reserved BARs,
+for such controllers, the corresponding BAR size in configfs will be ignored.
+

Binding pci-epf-test Device to EP Controller
--------------------------------------------
diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index b785d488c284..fda257e46920 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -63,6 +63,7 @@ static struct workqueue_struct *kpcitest_workqueue;
struct pci_epf_test {
void *reg[PCI_STD_NUM_BARS];
struct pci_epf *epf;
+ struct config_group group;
enum pci_barno test_reg_bar;
size_t msix_table_offset;
struct delayed_work cmd_handler;
@@ -76,6 +77,7 @@ struct pci_epf_test {
bool dma_private;
const struct pci_epc_features *epc_features;
struct pci_epf_bar db_bar;
+ size_t bar_size[PCI_STD_NUM_BARS];
};

struct pci_epf_test_reg {
@@ -102,7 +104,8 @@ static struct pci_epf_header test_header = {
.interrupt_pin = PCI_INTERRUPT_INTA,
};

-static size_t bar_size[] = { 512, 512, 1024, 16384, 131072, 1048576 };
+/* default BAR sizes, can be overridden by the user using configfs */
+static size_t default_bar_size[] = { 512, 512, 1024, 16384, 131072, 1048576 };

static void pci_epf_test_dma_callback(void *param)
{
@@ -1070,7 +1073,7 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
if (epc_features->bar[bar].type == BAR_FIXED)
test_reg_size = epc_features->bar[bar].fixed_size;
else
- test_reg_size = bar_size[bar];
+ test_reg_size = epf_test->bar_size[bar];

base = pci_epf_alloc_space(epf, test_reg_size, bar,
epc_features, PRIMARY_INTERFACE);
@@ -1142,6 +1145,87 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
pci_epf_test_free_space(epf);
}

+#define PCI_EPF_TEST_BAR_SIZE_R(_name, _id) \
+ static ssize_t pci_epf_test_##_name##_show(struct config_item *item, \
+ char *page) \
+ { \
+ struct config_group *group = to_config_group(item); \
+ struct pci_epf_test *epf_test = container_of(group, \
+ struct pci_epf_test, group); \
+ \
+ return sprintf(page, "%zu\n", epf_test->bar_size[_id]); \
+ }
+
+#define PCI_EPF_TEST_BAR_SIZE_W(_name, _id) \
+ static ssize_t pci_epf_test_##_name##_store(struct config_item *item, \
+ const char *page, size_t len) \
+ { \
+ struct config_group *group = to_config_group(item); \
+ struct pci_epf_test *epf_test = container_of(group, \
+ struct pci_epf_test, group); \
+ int val; \
+ int ret; \
+ \
+ ret = kstrtouint(page, 0, &val); \
+ if (ret) \
+ return ret; \
+ \
+ if (!is_power_of_2(val)) \
+ return -EINVAL; \
+ \
+ epf_test->bar_size[_id] = val; \
+ \
+ return len; \
+ }
+
+PCI_EPF_TEST_BAR_SIZE_R(bar0_size, BAR_0)
+PCI_EPF_TEST_BAR_SIZE_W(bar0_size, BAR_0)
+PCI_EPF_TEST_BAR_SIZE_R(bar1_size, BAR_1)
+PCI_EPF_TEST_BAR_SIZE_W(bar1_size, BAR_1)
+PCI_EPF_TEST_BAR_SIZE_R(bar2_size, BAR_2)
+PCI_EPF_TEST_BAR_SIZE_W(bar2_size, BAR_2)
+PCI_EPF_TEST_BAR_SIZE_R(bar3_size, BAR_3)
+PCI_EPF_TEST_BAR_SIZE_W(bar3_size, BAR_3)
+PCI_EPF_TEST_BAR_SIZE_R(bar4_size, BAR_4)
+PCI_EPF_TEST_BAR_SIZE_W(bar4_size, BAR_4)
+PCI_EPF_TEST_BAR_SIZE_R(bar5_size, BAR_5)
+PCI_EPF_TEST_BAR_SIZE_W(bar5_size, BAR_5)
+
+CONFIGFS_ATTR(pci_epf_test_, bar0_size);
+CONFIGFS_ATTR(pci_epf_test_, bar1_size);
+CONFIGFS_ATTR(pci_epf_test_, bar2_size);
+CONFIGFS_ATTR(pci_epf_test_, bar3_size);
+CONFIGFS_ATTR(pci_epf_test_, bar4_size);
+CONFIGFS_ATTR(pci_epf_test_, bar5_size);
+
+static struct configfs_attribute *pci_epf_test_attrs[] = {
+ &pci_epf_test_attr_bar0_size,
+ &pci_epf_test_attr_bar1_size,
+ &pci_epf_test_attr_bar2_size,
+ &pci_epf_test_attr_bar3_size,
+ &pci_epf_test_attr_bar4_size,
+ &pci_epf_test_attr_bar5_size,
+ NULL,
+};
+
+static const struct config_item_type pci_epf_test_group_type = {
+ .ct_attrs = pci_epf_test_attrs,
+ .ct_owner = THIS_MODULE,
+};
+
+static struct config_group *pci_epf_test_add_cfs(struct pci_epf *epf,
+ struct config_group *group)
+{
+ struct pci_epf_test *epf_test = epf_get_drvdata(epf);
+ struct config_group *epf_group = &epf_test->group;
+ struct device *dev = &epf->dev;
+
+ config_group_init_type_name(epf_group, dev_name(dev),
+ &pci_epf_test_group_type);
+
+ return epf_group;
+}
+
static const struct pci_epf_device_id pci_epf_test_ids[] = {
{
.name = "pci_epf_test",
@@ -1154,6 +1238,7 @@ static int pci_epf_test_probe(struct pci_epf *epf,
{
struct pci_epf_test *epf_test;
struct device *dev = &epf->dev;
+ enum pci_barno bar;

epf_test = devm_kzalloc(dev, sizeof(*epf_test), GFP_KERNEL);
if (!epf_test)
@@ -1161,6 +1246,8 @@ static int pci_epf_test_probe(struct pci_epf *epf,

epf->header = &test_header;
epf_test->epf = epf;
+ for (bar = BAR_0; bar < PCI_STD_NUM_BARS; bar++)
+ epf_test->bar_size[bar] = default_bar_size[bar];

INIT_DELAYED_WORK(&epf_test->cmd_handler, pci_epf_test_cmd_handler);

@@ -1173,6 +1260,7 @@ static int pci_epf_test_probe(struct pci_epf *epf,
static const struct pci_epf_ops ops = {
.unbind = pci_epf_test_unbind,
.bind = pci_epf_test_bind,
+ .add_cfs = pci_epf_test_add_cfs,
};

static struct pci_epf_driver test_driver = {

base-commit: c0dbaab0524adbc90d693aa15ab84354dd71acb2
--
2.52.0