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

Koichiro Den
2026-01-27T03:44:16Z

On Fri, Jan 23, 2026 at 07:07:48PM +0100, Niklas Cassel wrote:
> 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>

This is useful, thanks!
I've used this patch as a dependency for my series [1], and it works fine.

Tested-by: Koichiro Den <den@valinux.co.jp>

[1] https://lore.kernel.org/linux-pci/20260124145012.2794108-1-den@valinux.co.jp/

> ---
> 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
>